Preheat the oven to 325 degrees.
Heat the butter in an oven-proof skillet over medium heat on the stove.
Once the butter has melted, add the tomatoes and green onion to the skillet, and saute for a minute or two.
Add the spinach to the skillet and cook until wilted.
Stir in the garlic and chopped green chilis, and saute another 30 seconds.
In a mixing bowl, combine the egg whites, salt and pepper to taste, ricotta and cheddar cheese. Whisk to combine well.
Pour the egg white mixture over the veggies in the skillet, and bake for 35 minutes.