Preheat the oven to 425 degrees F.
Whisk together the eggs and ricotta in large mixing bowl and season with salt and pepper.
Heat 2 tablespoons olive oil in a medium skillet over medium heat. Add the garlic and stir for a few seconds, until fragrant. Add the egg-ricotta mixture and cook, stirring gently, until it starts to set, a few minutes. Transfer to the oven and bake until nearly set, about 12 minutes.
Meanwhile, heat 1 tablespoon olive oil in another medium skillet over medium-high heat. Add the sausage to the pan, breaking it up with the back of a wooden spoon; cook until cooked through and browned, 5 to 7 minutes. Add the onions, peppers and mushrooms, season with salt and pepper, and let cook for a few minutes. Remove from the heat and set aside until ready to use.
Remove the frittata from the oven and spoon the pizza sauce over the top. Top with the sausage mixture, pepperoni, mozzarella and Parmesan. Return to the oven and bake until cheese has melted, another 8 to 10 minutes.
Let the frittata cool in the pan for a few minutes before sliding it out onto a cutting board. Cut into slices and serve.
Add the tomatoes, olive oil, salt, basil and oregano to a food processor and puree until smooth. Pour the sauce into a medium saucepot and bring to a boil. Reduce the heat and hold at a simmer until ready to use.