Bell peppers are sliced in half, core and seeds removed. Slice mushrooms, dice onions, and combine eggs in a bowl and beat them.

Preheat your oven to 375 F.
Melt some cooking fat/butter in a skillet placed over a medium-heat.
Sauté the onion until soft, about 4 minutes, then add the mushrooms and tomatoes and cook about 2 minutes.
Add the spinach and cook until witted, about 1 or 2 minutes.
Season to taste with salt, pepper, and garlic powder.
Divide the vegetable mixture equally among the bell pepper halves
Top off each bell pepper half with some of the beaten eggs, and add the meat of your choice, if using.
Place the stuffed peppers in the oven, on a baking sheet, and bake for 40 minutes.