The cheese melts into the eggs and they become this creamy and luscious combination, with nutty notes from the Parmesan cheese and incredible flavor from the onion, garlic and marjoram. This is one you have to try! Buon Appetito!!!
Coat the bottom of a 10-inch skillet with 1 tablespoon of olive oil. Add the onion and marjoram and cook over medium heat for about 5 minutes. Then add the garlic and cook the onion is translucent and very aromatic, about 7 minutes total. Add 1 tablespoon of olive oil.
Meanwhile, in a medium bowl, whisk the eggs. Add the ricotta and Parmigiano-Reggiano and whisk together until creamy. Season with salt and pepper.
Pour the egg mixture into the skillet and stir to incorporate the onion. Cook until the eggs begin to set. You will notice the egg cooked around the edges of the pan. Transfer the skillet to the oven and bake for 12 to 15 minutes, until the frittata is set.
Turn the frittata out onto a serving platter and let cool. Drizzle the frittata with olive oil and serve at room temperature, with the tomato sauce on the side, or serve each slice on a ladle of sauce.