Preheat the oven to 350°F (175°C) and grease a muffin tin with cooking spray or olive oil.
In a large mixing bowl, whisk together the eggs and milk until well combined.
Add the chopped spinach, diced bell pepper, halved cherry tomatoes, red onion, shredded cheese, salt, pepper, garlic powder, and paprika to the egg mixture. Stir until all ingredients are evenly distributed.
Pour the egg mixture evenly into the prepared muffin tin, filling each cup about 2/3 full.
Bake in the preheated oven for 18-20 minutes, or until the muffins are puffed up and a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for 5 minutes before gently removing them and placing them on a wire rack to cool completely.
Notes
Serve warm on a colorful platter, garnished with fresh herbs like parsley or chives.