Preheat the oven to 325 degrees.

Heat the butter in an oven-proof skillet over medium heat. Once melted, add the cherry tomatoes and green onions and sauté for one to two minutes.

Add the spinach to the skillet and cook until wilted. Stir in the minced garlic and chopped green chilis and sauté for about 30 seconds.

In a mixing bowl, whisk together the liquid egg whites, ricotta cheese, cheddar cheese, salt, and pepper until smooth.

Pour the egg white mixture over the vegetables in the skillet. Transfer the skillet to the oven and bake for about 35 minutes, until the frittata is set.