Classic Onion Tart

1. Cook Onions

Heat the olive oil in a low-sided, heavy-bottomed pan over medium heat. Add the sliced onions and thyme sprigs. Cook slowly, stirring frequently, for about 20 to 30 minutes until onions are soft and sweet.

2. Chill Dough

Roll out the tart and pie dough and place it on a parchment-lined baking sheet. Chill in the refrigerator for 10 minutes.

3. Prepare Tart Base

Spread the cooled onions over the center of the chilled dough, leaving a border around the edges. Fold the edges of the dough over the onions to create a rustic crust.

4. Apply Egg Wash

Whisk together the egg and milk to create an egg wash. Brush this over the folded edges of the dough.

5. Bake Tart

Bake the tart on the bottom rack of a preheated oven at 375°F for 45 to 50 minutes, until the crust is golden brown.