French Onion Tart with Cheesy Thyme Pastry Recipe

In a large skillet, melt the butter over medium heat. Add the sliced onions and cook until caramelized, stirring occasionally, for about 15-20 minutes. Stir in the sugar and cook for an additional 5 minutes. Remove from heat and set aside.

In a food processor, combine the flour, salt, dried thyme, and cold diced butter. Pulse until the mixture resembles coarse crumbs. Gradually add the ice water, 1 tablespoon at a time, until the dough comes together in a ball.

Wrap the pastry dough in plastic wrap and refrigerate for at least 30 minutes.

Preheat the oven to 400°F (200°C).

Roll out the chilled pastry dough on a lightly floured surface to fit a 9-inch tart pan. Press the dough into the pan and trim any excess.

Sprinkle half of the shredded Gruyere cheese over the bottom of the tart shell. Spread the caramelized onions evenly over the cheese. Sprinkle the remaining Gruyere cheese on top.

Bake in the preheated oven for 25-30 minutes, or until the pastry is golden and the cheese is melted and bubbly.

Allow the tart to cool for a few minutes before slicing and serving.