Preheat the oven to 375°F (190°C). Roll out the pie crust and press it into a 9-inch pie dish. Trim the edges and prick the bottom with a fork.

Blind bake the crust: Line the crust with parchment paper and fill with pie weights or dried beans. Bake for 10 minutes, then remove the weights and parchment and bake for another 5 minutes.

Sauté the vegetables: In a pan, heat a little oil over medium heat. Add onions and bell peppers, cooking until softened. Add spinach and cook until wilted. Remove from heat and let cool slightly.

Prepare the custard: In a bowl, whisk together eggs, heavy cream, salt, black pepper, and nutmeg until smooth.

Assemble the quiche: Spread the sautéed vegetables evenly over the pre-baked crust. Sprinkle shredded cheese on top. Pour the egg custard mixture over the vegetables and cheese.

Bake the quiche: Place the pie dish on a baking sheet and bake for 35-40 minutes, or until the custard is set and the top is golden brown. Let cool for 10 minutes before slicing.