In a large skillet (mine is a 12 inch cast iron), place butter, onions, and a dash of salt on low to medium heat. We are trying to caramelize the onions so this takes quit awhile. This also gives it a much richer flavor. If you don't have a ton of time than just saute until soft.

While the onions are cooking, rough chop the spinach, grate the cheese (if not using pre-grated cheese), and dice the pepper.

Preheat oven to 400 degrees.In a large bowl, crack the eggs and whisk in the milk, salt, and pepper.

After the onions are pretty caramelized add in the green peppers and cook until softened.

Add in the spinach and stir until wilted.

Pour egg and milk mixture into pan and allow to cook for 3-4 minutes mixing the eggs with the spinach and pulling the spinach up to the top.

Top with cheese and bake in the oven for 15-20 minutes until completely cooked.

If you want it to be a little browner, pop it into under the broiler for 2-3 minutes. Allow to cook for a few minutes, and serve.