1/2 cup (50g) grated Gruyère or Swiss cheese (optional)
1
Prepare the Pastry:
Combine flour and salt in a large bowl. Add the butter and use a pastry blender or fingers to mix until the mixture resembles coarse crumbs.
Gradually add ice water, stirring until the dough comes together. Form into a disk, wrap in plastic, and chill for at least 1 hour.
2
Pre-bake the Crust:
Preheat the oven to 375°F (190°C).
Roll out the dough to fit a 9-inch (23 cm) tart pan. Press the dough into the pan, trim the excess, and prick the bottom with a fork.
Line with parchment paper and fill with pie weights or dried beans. Bake for 20 minutes, remove weights and paper, and bake for another 10 minutes until lightly golden.
3
Prepare the Filling:
In a large skillet, heat butter and oil over medium heat. Add onions, sugar, and salt. Cook, stirring occasionally, until onions are caramelized, about 30-40 minutes. Stir in thyme.
4
Assemble the Tart:
Spread the caramelized onions evenly over the pre-baked crust.
In a bowl, whisk together eggs, cream, salt, and pepper. Pour this mixture over the onions. Sprinkle with cheese if using.
5
Bake:
Bake at 375°F (190°C) for 25-30 minutes, or until the custard is set and the top is golden brown.
6
Serve:
Let the tart cool slightly before slicing. Serve warm or at room temperature.
Ingredients
For the Pastry:
1 1/4 cups all-purpose flour
1/2 teaspoon salt
1/2 cup (113g) cold unsalted butter, cubed
3-4 tablespoons ice water
For the Filling:
2 tablespoons unsalted butter
2 tablespoons olive oil
2 lbs (about 900g) onions, thinly sliced
1 teaspoon sugar
1 teaspoon salt
2 teaspoons thyme, minced
3 large eggs
1 cup (240ml) heavy cream
Salt and pepper to taste
1/2 cup (50g) grated Gruyère or Swiss cheese (optional)
Directions
1
Prepare the Pastry:
Combine flour and salt in a large bowl. Add the butter and use a pastry blender or fingers to mix until the mixture resembles coarse crumbs.
Gradually add ice water, stirring until the dough comes together. Form into a disk, wrap in plastic, and chill for at least 1 hour.
2
Pre-bake the Crust:
Preheat the oven to 375°F (190°C).
Roll out the dough to fit a 9-inch (23 cm) tart pan. Press the dough into the pan, trim the excess, and prick the bottom with a fork.
Line with parchment paper and fill with pie weights or dried beans. Bake for 20 minutes, remove weights and paper, and bake for another 10 minutes until lightly golden.
3
Prepare the Filling:
In a large skillet, heat butter and oil over medium heat. Add onions, sugar, and salt. Cook, stirring occasionally, until onions are caramelized, about 30-40 minutes. Stir in thyme.
4
Assemble the Tart:
Spread the caramelized onions evenly over the pre-baked crust.
In a bowl, whisk together eggs, cream, salt, and pepper. Pour this mixture over the onions. Sprinkle with cheese if using.
5
Bake:
Bake at 375°F (190°C) for 25-30 minutes, or until the custard is set and the top is golden brown.
6
Serve:
Let the tart cool slightly before slicing. Serve warm or at room temperature.
