STEP 1: Prep.
Preheat oven to 350 deg.
Grease deep baking dish. (2 qt.)
Cook sausage, then slice.

STEP 2: Mix ingredients.
Beat eggs. Mix in ricotta, mozzarella cheese, garlic powder, pepper, and salt.
(Cover and refrigerate if baking the next day.)

STEP 3: Layering ingredients.
Start by pouring the first layer of egg mixture, then a sausage and optional items if used, then another egg mixture layer, then a sausage layer and optional items, and finally top with the balance of the egg mixture.

STEP 4: Bake
Place foil on a cookie sheet, in case of spills, then place the uncooked frittata on top. If you find you have filled your dish to the brim, add a little foil strip barrier around the dish lip. You can remove the foil once it begins to set. As you can see in the photos, I filled mine to the brim and once it began to set, there was no spillage.

Bake 45-55 minutes, or until a knife inserted in the center comes out clean.
Rest 30 minutes before slicing. Best when served warm.