Preheat your oven to 400 degrees.
I sprayed my 8 inch iron skillet. You can use any comparable baking dish.
Place 1 TBSP butter in skillet/dish and set in the oven to melt while you mix up the ingredients.
In a large bowl, add the chopped veggies, beans, cheese and spinach.
In a separate bowl, whisk the 3 eggs until smooth and pour over the veggies in the bowl.
Stir until well combined and season with salt and pepper.
Remove pan from the oven and pour in the fritatta mixture.
Bake about 12-15 minutes until eggs are set.
Remove from pan to plates and serve with a side of salsa or salsa verde.