Preheat your oven to 375°F (190°C).

If making a homemade crust, combine flour, cold butter, and pinch of salt using a pastry cutter. Add cold water gradually until dough holds. Roll out and fit into a pie dish. Blind bake for 10-15 minutes.

Cube butternut squash, toss with olive oil, salt, and pepper. Roast on a baking sheet at 400°F (200°C) for 25 minutes until tender.

Sauté finely chopped onions in a skillet with olive oil over medium heat for 5-7 minutes until translucent.

Whisk together eggs, heavy cream, grated Gruyère cheese, chopped sage, salt, and pepper in a large mixing bowl.

Layer the roasted squash and sautéed onions in the blind-baked crust. Pour the egg mixture over the top.

Bake quiche in the oven for 30-35 minutes until the filling is set and edges are golden brown.

Allow quiche to cool for about 10 minutes before slicing and serving warm.