Preheat oven to 350.
Heat 1 tablespoon of olive oil in 10-inch cast iron pan on medium heat. Add onions and peppers and cook until softened, about 5 minutes. Add mushrooms and cook until softened and then add tomatoes.
While veggies are cooking, whisk eggs and sour cream in a large bowl. Mix in 3/4 cup of cheese and season with salt and pepper.
Add remaining oil to the skillet and pour the egg mixture evenly over the veggies. Cook without stirring until the edges set, about 5 minutes.
Top with remaining cheese and place pan in the oven. Bake until center is set, 20-30 minutes. Be careful not to over-bake.
This frittata is customizable. You can use whatever veggies and cheese you have on hand. Leftover potatoes or any other cooked veggies also work well.
We recommend using organic ingredients whenever possible.