Onion Tart

This easy Onion Tart comes together with a crisp shortcrust base, slow-cooked onions, and a creamy, cheesy filling that bakes to a golden finish. Every slice has gentle sweetness from the onions and a soft, custard-like texture. It’s great served warm or cold.

I used to think onion tarts were fancy restaurant food until I realized how simple they actually are to make at home.

This onion tart has elegant French bistro vibes, but with zero pretension and all the flavor. The caramelized onions get sweet and delicious, the cheesy custard filling is smooth and creamy, and that homemade shortcut crust? Perfection! I’ve made this for everything from casual get-togethers to actual dinner parties, and it never misses.

If you’re looking for a recipe that makes you look like you have your life together (even if you don’t), this is the one. Trust me on this.

Why I love this recipe

• The caramelized onions are the star here – it’s so satisfying to watch them go from sharp and strong to sweet and golden.
• It looks fancy but comes together with pantry staples – I always have these ingredients on hand.
• The buttery homemade crust makes all the difference – store-bought just can’t compete with that flaky texture.
• It’s versatile enough for any occasion – I’ve served this at brunches, dinner parties, and even packed it for picnics.
• The leftovers taste amazing – sometimes I think it’s even better the next day when the flavors have melded together.
• It fills my kitchen with the most incredible aroma – those caramelizing onions are pure heaven.

If you have leftover onions, be sure to check out my Crispy Baked Onion Rings or my Salisbury Steak with Onion Gravy.

Ingredients

• crust: all-purpose flour, cold unsalted butter, egg, salt, and a splash of cold water – creating a tender, flaky shortcrust base.
• filling: onions slowly softened in butter, heavy cream, eggs, and shredded cheese perfectly seasoned with salt, pepper, and a pinch of nutmeg

Step by step

For the crust:

1. In a large bowl, mix the flour, salt, and butter, rubbing the mixture with your fingers until it resembles fine breadcrumbs.
2. Add the egg and a bit of cold water, then gently knead until the dough comes together and feels smooth.
3. Shape the dough into a ball, wrap it in cling film, and chill it in the refrigerator for 30 minutes.

For the filling:

1. Slice the onions into thin half rings.
2. Melt the butter over medium heat in a skillet. Add the onions and sauté until soft and caramelized (about 20 minutes). Stir frequently to avoid burning.
3. In a separate bowl, whisk the eggs with the cream. Stir in the cheese, along with salt, pepper, and a pinch of nutmeg.

Assembling the tart:

1. Roll out the chilled dough and press it into a 9-inch tart pan, making sure to form the edges. Use a fork to poke holes in the bottom.
2. Cover the crust in parchment paper and fill with pie weights or dried beans and pre-bake the crust in a preheated oven at 350°F for 10 minutes. Remove from oven and carefully remove parchment paper and weights/beans.
3. Spread the caramelized onions into the crust, then pour the egg and cheese mixture over the top.
4. Bake at 350°F for another 25-30 minutes, until the filling is golden and set.
5. Allow the tart to rest for a few minutes before cutting. It’s delicious warm or chilled.

Variations

Give this onion tart a new twist by adding crispy bacon or pancetta for a smoky flavor. Use a combination of Gruyère and sharp Cheddar to make the cheese taste richer

Serving suggestions

Serve it warm as a main course alongside a crisp green salad dressed with vinaigrette. It’s also perfect for brunch paired with Grapefruit Mimosas for brunch or cut into smaller wedges as an elegant appetizer at cocktail parties.

Storage

Store leftover onion tart covered or in an air-tight container in the refrigerator for up to 3 days. To warm it up, place it in a 300°F oven for 10–15 minutes so the crust stays crisp.

You can also enjoy it cold from the fridge, which is honestly one of my favorite ways to eat it the next day. If you want to freeze it, wrap it tightly in plastic wrap and then foil. It will keep for up to 2 months. Let it thaw in the fridge overnight before reheating.

For the best texture, I like freezing the tart before the final bake. Prepare everything, freeze it unbaked, and bake it straight from frozen, adding around 10–15 extra minutes to the cooking time.

If you try this recipe please comment and rate it below, I love hearing from you!