Preheat the oven to 375°F (190°C). Grease a 9-inch pie dish with butter.

In a large skillet, cook the bacon until crispy. Remove and crumble, reserving 1 tablespoon of bacon fat in the pan.

In the same skillet, sauté the onions and bell peppers in the bacon fat until softened, about 5 minutes. Add the spinach and cook until wilted, about 2 minutes more. Set aside to cool slightly.

In a large bowl, whisk together eggs, heavy cream, garlic powder, thyme, salt, and pepper until well combined.

Spread the sautéed vegetables evenly in the bottom of the greased pie dish. Sprinkle the crumbled bacon over the vegetables.

Pour the egg mixture over the vegetables and bacon. Sprinkle the shredded cheese evenly over the top.

Bake for 30-35 minutes, or until the quiche is set and the top is golden brown. The center should be slightly jiggly but not liquid.

Allow to cool for 5-10 minutes before slicing and serving.