Preheat the oven to 375 F.
Melt some coconut oil in a skillet over medium heat, and cook the onion and garlic until soft, 2 to 3 minutes.
½ cup yellow onion, 2 tbsp. coconut oil, 2 garlic cloves
Add the bell pepper, mushrooms, and tomato and cook until soft, about 2 to 5 minutes.
1 bell pepper, ½ cup mushrooms, 1 small tomato
Add the spinach, season everything to taste, and cook for another minute and set aside until cool.
1 cup fresh spinach
Whisk the eggs in a bowl, add the cold vegetable mixture to the eggs, season to taste, and whisk everything until well incorporated.
8 eggs, Sea salt and freshly ground black pepper
Fill each muffin tin about ⅔ full with the egg mixture.
Place in the oven and bake for 18 to 20 minutes or until set.
Makes about 12 muffins.