Preheat your oven to 375°F (190°C). Fit the pie crust into a 9-inch pie dish, prick the bottom, and pre-bake for 15 minutes.

Peel and cube the butternut squash. Toss with olive oil, salt, and pepper, and roast for about 25-30 minutes until tender.

Finely chop the onion and sauté in olive oil for 5-7 minutes until translucent.

In a mixing bowl, whisk together the eggs and heavy cream, then fold in the roasted squash, onions, and Gruyère cheese.

Pour the filling into the pre-baked crust and bake for 40-45 minutes until the custard is set and golden brown.

Let the quiche cool for at least 10 minutes before slicing. Serve warm or at room temperature.