Preheat the oven to 350 °F/ 180 °C , middle rack position.
Sift the flour into a large bowl & add baking powder, salt, pepper, Parmesan cheese, mozzarella cheese and give it a light stir with a spatula.
In another large bowl, whisk the eggs first and then add green peas, carrots, red & yellow bell peppers and spinach. Stir, lightly with a spatula, until it's combined with the eggs.
Add the dry ingredients into the wet ingredients. Stir it all in & combine well with a spatula.
Place paper muffin liners into the muffin tin and spray them with vegetable oil. Spoon the batter into a muffin tin and bake in the preheated oven for 25 minutes, or until the toothpick comes out clean and the tops are golden brown. In needed, bake for an additional 5–10 minutes if the toothpick comes out wet with batter.
Remove the muffins from the oven and place the tin on a protective (wooden) board. Let the muffins rest for about 10 minutes inside the tin. Then remove the muffins from the tin and serve warm with garden salad or refrigerate for next morning use.