Appetizer · Main Course · French · Dinner ·

French Caramelized Onion and Gruyère Tart with Thyme

Name: French Caramelized Onion and Gruyère Tart with Thyme
Prep time: 35 min
Cook time: 105 min
Total time: 140 min
Yield: 6 servings
Cuisine: Appetizer
Ingredients: 1 1/2 cups all-purpose flour; 1/2 cup unsalted butter, cubed and chilled; 1/4 tsp salt; 3 to 4 tbsp cold water; 3 large sweet onions, thinly sliced; 2 tbsp unsalted butter; 1 tbsp olive oil; 1/2 tsp salt; 1/4 tsp black pepper; 1 tsp fresh thyme, chopped; 1 1/2 cups Gruyère cheese, grated; 1 egg, beaten; 1/4 cup heavy cream; Fresh thyme sprigs

A classic French tart featuring rich caramelized onions balanced with the nutty flavor of Gruyère, accented by fresh thyme.

5(242 reviews)

·By Ethan Brooks·October 25, 2025

French Caramelized Onion and Gruyère Tart with Thyme — Appetizer served and photographed from above

Prep

35 min

Cook

1 h 45 min

Difficulty

Intermediate

Serves

Ingredients

Servings

For the Tart Crust

For the Caramelized Onion Filling

For the Gruyère Topping

For the Finishing Touch

Nutrition

Per serving

Calories: 481 kcal
Protein: 13.2 g
Carbs: 31.2 g
Fat: 34.3 g
Fiber: 2.2 g

Whole recipe

Total

Calories: 2887 kcal
Protein: 79 g
Carbs: 187 g
Fat: 206 g
Fiber: 13 g

Breakdown by ingredient▾

Ingredient	Cal	P	C	F	Fib
1 1/2 cups all-purpose flour	684	18	140	2	5
1/2 cup unsalted butter cubed and chilled	813	1	0	92	0
1/4 tsp salt	0	0	0	0	0
3 to 4 tbsp cold water	0	0	0	0	0
3 large sweet onions thinly sliced	180	4	43	0	7
2 tbsp unsalted butter	204	0	0	23	0
1 tbsp olive oil	119	0	0	14	0
1/2 tsp salt	0	0	0	0	0
1/4 tsp black pepper	2	0	0	0	1
1 tsp fresh thyme chopped	1	0	0	0	0
1 1/2 cups Gruyère cheese grated	607	48	0	48	0
1 egg beaten	72	6	1	5	0
1/4 cup heavy cream	204	2	3	22	0
Fresh thyme sprigs	1	0	0	0	0

These are estimates, not dietary advice.

Preparation

Get these tasks done before you start cooking.

Making the Tart Crust

1
Combine dry ingredients
In a bowl, combine flour and salt.
2
Cut in butter
Add the cubed butter and mix until coarse crumbs form.
3
Form dough
Gradually add water, one tablespoon at a time, until the dough comes together.

Caramelizing the Onions

1
Heat fat
In a large skillet, heat butter and olive oil over medium heat.
2
Cook onions
Add onions, salt, and pepper, cooking until onions are deeply caramelized, about 35-40 minutes.
Tip: Ensure the onions are fully caramelized for the deepest flavor. Stir occasionally for even cooking and avoid burning.
3
Add thyme
Stir in the thyme and set aside to cool slightly.

How to Make French Caramelized Onion and Gruyère Tart with Thyme

Total time: 2 h 20 min · Yields 6 servings

1
Blind Baking the Crust
Roll out the dough, fit it into a tart pan, and bake at 375°F (190°C) for 10 minutes with pie weights.
2
Bake Crust
Remove weights and bake for another 5 minutes until lightly golden.
3
Fill and Bake Tart
Spread caramelized onions in crust, pour the egg and cream mixture over, then top with grated Gruyère and bake for 25 minutes.