Combine all of the marinara ingredients in a medium saucepan and place over medium-high heat and stir until it is completely mixed. Decrease the heat to a simmer and cook for 5 minutes. Keep on low heat until you are ready to use it.
In a large bowl, combine the beef, breadcrumbs, cheese, onion, milk, rosemary, parsley, basil, salt, pepper, garlic and egg. Use your hands to gently mix until blended, but don’t overmix.
Using a 2-tablespoon scoop, portion out the meatballs and place them on a baking sheet or a plate. Lightly oil your hands and roll them into balls.
Preheat the oven to 375ºF.
Place a 12-inch cast-iron skillet or other oven safe skillet over medium heat. Add the olive oil to the skillet. Place the meatballs in the skillet. Once the meatballs are browned on one side, turn the meatballs over. Pour the marinara over the meatballs. Place the skillet in the preheated oven. Bake for 15 minutes, or until the meatballs are cooked through.
Sprinkle the mozzarella and Parmesan cheese over the meatballs and return the skillet to the oven. Continue baking until the cheese is melted, 3 to 5 minutes. Remove from the oven and sprinkle with the basil and parsley before serving.
