In a mixing bowl, combine flour, salt, and chopped herbs. Add cold butter and mix until crumbly. Stir in ice water until dough forms.

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

In a skillet, sauté sliced onions over medium heat until caramelized, about 20 minutes.

Add thyme, black pepper, and cream to the onions, stirring to combine.

Preheat the oven to 400°F (200°C). Roll out the chilled dough on a floured surface.

Transfer the dough to a baking sheet, add the onion mixture, and sprinkle with gruyere cheese.

Fold the edges of the dough over the filling and bake for 25-30 minutes until golden brown.