Caramelized Onion and Gruyere Galette with Thyme

**Make the dough:** In a large bowl, whisk together flour and salt. Cut in cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Gradually add ice water, 1 tablespoon at a time, mixing until the dough just comes together. Flatten into a disc, wrap in plastic wrap, and refrigerate for at least 30 minutes.

**Caramelize the onions:** While the dough chills, heat olive oil in a large skillet over medium-low heat. Add sliced onions and salt. Cook, stirring occasionally, until the onions are very soft, golden brown, and caramelized, about 20-25 minutes. Stir in thyme leaves during the last few minutes of cooking.

**Assemble the galette:** Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper. On a lightly floured surface, roll out the dough into a 12-inch circle. Transfer the dough to the prepared baking sheet.

Spread the caramelized onions evenly over the dough, leaving a 2-inch border. Sprinkle shredded Gruyere cheese over the onions.

Fold the edges of the dough over the filling, pleating as you go. Brush the crust with beaten egg.

Bake for 25-30 minutes, or until the crust is golden brown and the cheese is melted and bubbly. Let cool slightly before slicing and serving.