I just made a Caramelized Onion Pie that somehow turns simple onions into a show-stopping flaky centerpiece and I’m not even sorry.

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I can’t get over how obsessed I am with caramelized onion tart. I love that sweet, sneaky melt of onions on a crisp shell.

I make it at holiday gatherings because it’s not the usual turkey sides and it reads as fancy without being precious. The smell of yellow onions collapsing into sticky sweet gold makes me drool.

I pair it with flaky puff pastry because I’m greedy. Caramelized Onion Pie vibes, but quieter, grown-up.

It’s my go-to Puff Pastry Side Dish for Christmas Party Food Main Dish situations. Bring it and watch people fight for the last slice now.

Ingredients

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Puff pastry: flaky base that’s buttery and gives the tart crisp lift.
Yellow onions: sweet, jammy heart of the tart once they’re soft.
Unsalted butter: adds richness and helps caramelize those onions nicely.
Olive oil: keeps things from burning and adds a subtle fruitiness.
Granulated sugar: speeds caramelization, makes the onions taste sweeter.
Kosher salt: brings out onion sweetness; don’t forget a finishing pinch.
Black pepper: a little bite to cut through the richness.
Thyme: earthy herb that pairs perfectly with onions and cheese.
Gruyere cheese: melty, nutty top that gives savory depth.
Goat cheese: tangy creaminess, optional but you’ll probably want it.
Egg wash: basically makes the pastry shine and turn golden brown.

Ingredient Quantities

1 sheet puff pastry, thawed (about 9 x 12 inches)

4 large yellow onions, thinly sliced (about 2 pounds)

2 tablespoons unsalted butter

1 tablespoon olive oil

1 teaspoon granulated sugar

1/2 teaspoon kosher salt, plus more for finishing

1/4 teaspoon freshly ground black pepper

1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme

3/4 cup grated Gruyere cheese (about 3 ounces)

2 ounces goat cheese, crumbled (optional, but you might want it)

1 large egg beaten with 1 tablespoon water for egg wash (optional)

How to Make this

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1. Preheat oven to 400 F. Line a baking sheet with parchment or lightly flour the sheet so the puff pastry wont stick.

2. Heat a large skillet over medium low heat and add the butter and olive oil. When butter melts add the thinly sliced onions, 1 teaspoon granulated sugar, 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Stir to coat.

3. Cook the onions slowly, stirring every few minutes, until they are deeply golden and jammy, about 30 to 40 minutes. If they start to stick, add a splash of water and scrape up the brown bits. Stir in the thyme toward the end.

4. While the onions cook, unfold the thawed puff pastry on a lightly floured surface and gently roll to a roughly 10 x 14 inch rectangle if needed. Transfer to the prepared baking sheet.

5. Use a sharp knife or a pizza cutter to score a 1/2 inch border around the edge of the pastry without cutting all the way through. This helps the edges puff. Prick the center area lightly with a fork so the middle wont puff too much.

6. Spread the caramelized onions evenly across the center of the pastry, leaving the scored border clear. Sprinkle the grated Gruyere evenly over the onions and dot with crumbled goat cheese if using.

7. If using egg wash, beat the egg with 1 tablespoon water and brush the pastry border lightly. This will give a nice golden finish. Sprinkle a little extra flaky salt and a pinch of black pepper over the tart.

8. Bake until the crust is puffed and golden and the cheese is melted, about 20 to 25 minutes. Rotate the pan halfway through if your oven cooks unevenly.

9. Let the tart cool for 5 to 10 minutes so it firms up, then cut into squares or slices. Scatter a few extra thyme leaves and a little more flaky salt before serving. Enjoy warm or at room temperature.

Equipment Needed

1. Oven (set to 400 F)
2. Rimmed baking sheet plus parchment paper or a little flour so the pastry wont stick
3. Large skillet for slow caramelizing the onions
4. Wooden spoon or heatproof spatula to stir and scrape the pan
5. Sharp knife or pizza cutter for scoring and slicing
6. Rolling pin to gently shape the puff pastry
7. Box grater for the Gruyere
8. Fork to prick the pastry center and a small bowl to beat the egg wash
9. Pastry brush for brushing the egg wash and a pair of tongs or a spatula to lift slices

FAQ

Q: Can I make the onions ahead of time and store them?

A: Yes. Cook the onions until soft and golden, cool completely, then store in an airtight container in the fridge for up to 4 days. Warm them gently before assembling so the tart bakes evenly.

Q: I do not have hours to caramelize onions. Any shortcuts?

A: Use a pinch more sugar and a splash of balsamic or water, cook on medium heat and stir more often. You can also microwave sliced onions for 5 to 7 minutes to soften them first, then finish browning in the pan. It won’t be exactly the same, but it helps when you are short on time.

Q: Can I swap the Gruyere and goat cheese?

A: Totally. Sharp cheddar, fontina, or emmental work well in place of Gruyere. If you skip goat cheese, add a little extra grated cheese or a smear of ricotta for creaminess. The tart is forgiving.

Q: My guests are gluten free. Can I make this tart without regular puff pastry?

A: Yes, use a refrigerated gluten free puff pastry if you can find it. Another option is a savory shortcrust made with gluten free flour. Baking times might change a few minutes, so watch for golden edges.

Q: Can I freeze this tart or the assembled tart before baking?

A: You can freeze cooked onion filling in a freezer bag for up to 3 months. Assembled unbaked tarts freeze okay too if wrapped tightly, but thaw in the fridge before baking and add a few extra minutes in the oven. Baked tart also freezes well, reheat from frozen at 350°F until warmed through.

Q: How do I reheat leftovers so the crust stays crisp?

A: Reheat in a 350 to 375°F oven for 10 to 15 minutes. A skillet on medium-low with a lid works too for a quick crisp bottom. Avoid the microwave unless you dont mind a soggy crust.

Caramelized Onion Tart (Christmas Recipe & Thanksgiving Recipe) Substitutions and Variations

4 large yellow onions: swap with 6 to 8 shallots for a sweeter, more delicate flavor, or use 3 large red onions for a slightly sharper, fruitier bite.
3/4 cup grated Gruyere: try sharp cheddar for a bolder, punchier taste, or use Comté or young Parmesan if you want a nutty, savory melt.
2 ounces goat cheese: omit it for a cleaner, creamier tart, or replace with 2 ounces ricotta or mascarpone for mild creaminess without tang.
1 sheet puff pastry: use a sheet of phyllo stacked and brushed with butter for extra flake, or substitute a pre-made savory pie crust for a sturdier base.

Pro Tips

1) Caramelize the onions low and slow, dont rush it. If they start sticking, add a splash of water and scrape the brown bits, those bits are flavor so dont throw them away.

2) Chill the puff pastry a little before baking if it feels too soft, that helps the layers puff up and stop it from getting soggy under the onions. Also prick the center with a fork so the middle stays flat.

3) Don’t overload with cheese, a thin even layer melts better and lets the sweetness of the onions shine. If you like a tangy hit, dot with goat cheese after the tart comes out so it stays bright.

4) Rotate the pan halfway through baking and let the tart cool 5 to 10 minutes on the sheet before cutting, it firms up and cuts cleaner. Sprinkle flaky salt right before serving, it makes a big difference.

Caramelized Onion Tart (Christmas Recipe & Thanksgiving Recipe)

Recipe by Francis Mead

0.0 from 0 votes

I just made a Caramelized Onion Pie that somehow turns simple onions into a show-stopping flaky centerpiece and I’m not even sorry.

Servings

servings

Calories

446

kcal

Equipment: 1. Oven (set to 400 F)
2. Rimmed baking sheet plus parchment paper or a little flour so the pastry wont stick
3. Large skillet for slow caramelizing the onions
4. Wooden spoon or heatproof spatula to stir and scrape the pan
5. Sharp knife or pizza cutter for scoring and slicing
6. Rolling pin to gently shape the puff pastry
7. Box grater for the Gruyere
8. Fork to prick the pastry center and a small bowl to beat the egg wash
9. Pastry brush for brushing the egg wash and a pair of tongs or a spatula to lift slices

Ingredients

1 sheet puff pastry, thawed (about 9 x 12 inches)
4 large yellow onions, thinly sliced (about 2 pounds)
2 tablespoons unsalted butter
1 tablespoon olive oil
1 teaspoon granulated sugar
1/2 teaspoon kosher salt, plus more for finishing
1/4 teaspoon freshly ground black pepper
1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme
3/4 cup grated Gruyere cheese (about 3 ounces)
2 ounces goat cheese, crumbled (optional, but you might want it)
1 large egg beaten with 1 tablespoon water for egg wash (optional)

Directions

Preheat oven to 400 F. Line a baking sheet with parchment or lightly flour the sheet so the puff pastry wont stick.
Heat a large skillet over medium low heat and add the butter and olive oil. When butter melts add the thinly sliced onions, 1 teaspoon granulated sugar, 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Stir to coat.
Cook the onions slowly, stirring every few minutes, until they are deeply golden and jammy, about 30 to 40 minutes. If they start to stick, add a splash of water and scrape up the brown bits. Stir in the thyme toward the end.
While the onions cook, unfold the thawed puff pastry on a lightly floured surface and gently roll to a roughly 10 x 14 inch rectangle if needed. Transfer to the prepared baking sheet.
Use a sharp knife or a pizza cutter to score a 1/2 inch border around the edge of the pastry without cutting all the way through. This helps the edges puff. Prick the center area lightly with a fork so the middle wont puff too much.
Spread the caramelized onions evenly across the center of the pastry, leaving the scored border clear. Sprinkle the grated Gruyere evenly over the onions and dot with crumbled goat cheese if using.
If using egg wash, beat the egg with 1 tablespoon water and brush the pastry border lightly. This will give a nice golden finish. Sprinkle a little extra flaky salt and a pinch of black pepper over the tart.
Bake until the crust is puffed and golden and the cheese is melted, about 20 to 25 minutes. Rotate the pan halfway through if your oven cooks unevenly.
Let the tart cool for 5 to 10 minutes so it firms up, then cut into squares or slices. Scatter a few extra thyme leaves and a little more flaky salt before serving. Enjoy warm or at room temperature.

Notes

Below you’ll find my best estimate of this recipe’s nutrition facts. Treat the numbers as a guide rather than a rule—great food should nourish both body and spirit. Figures are approximate, and the website owner assumes no liability for any inaccuracies in this recipe.