Roll out the pre-made pie crust and place it into a 9-inch tart pan or pie dish. Prick the base with a fork and chill in the fridge for 15 minutes.

Heat a skillet over medium heat. Add diced bacon and cook until crispy, about 5-7 minutes. Remove excess fat, then add diced onion and sauté for another 5 minutes until soft.

Preheat oven to 375°F (190°C). Line the crust with parchment paper and fill with pie weights or dried beans. Bake for 10-12 minutes until edges are golden brown.

In a bowl, whisk together eggs, heavy cream, salt, and black pepper until smooth.

Gently stir in bacon, onions, and shredded Gruyère cheese.

Pour the filling into the pre-baked crust and bake for 25-30 minutes until set and lightly golden.

Allow to cool for 10 minutes before serving warm.