Cook the chorizo in an oven safe pan on medium heat.
Remove cooked meat and half of the oil, then sauté the onions in the remaining oil.
Mix the ingredients you would like to incorporate into your frittata into a bowl. We used pasture-raised eggs, shredded cheddar cheese, the cooked onions, chorizo and cherry tomatoes. Season with a little salt and pepper.
Pour ingredients from bowl into the oven safe pan you used to cook your chorizo and onions, and stick in a 375 degree oven for as long as it takes for your eggs to set. (Jiggle it around until it no longer moves like jello in the center.)