Add cooked sausage to bottom of buttered 9 x 13 baking dish. NOTE: My sausage left a slight amount of grease in the bottom of pan that I used to cook the veggies in, but, there was no need to drain. Feel free to drain if yours produces an excess of grease to make it healthier.
Top with a layer of fresh spinach.
Chop onion, peppers, and mushrooms and add to skillet that sausage was cooked in. If using fresh tomatoes, slice and add to the veggies. Cook until tender. If using diced canned tomatoes, make sure that they are drained before adding them to the other vegetables to cook.Add salt and pepper, as desired.
Add cooked layer of vegetables on top of spinach.
Whisk eggs until beaten well. I added a little more salt and pepper to the eggs. Pour over vegetable layer.
Top with cheese.
Bake in preheated oven until center is set--about 35 minutes or so, until center is set.
Notes
Low in carbs, this Keto Friendly frittata is quick and easy and a hit with brunch guests!TIP: Make it easy and make it the day before and just bake before serving. Perfect for Christmas or New Year's morning!