Step 2: Brown the Beef and Build the Meat Sauce - Set a
large skillet over medium heat and add the ground beef and diced onion. Cook them together, breaking the beef into small crumbles with a
wooden spoon, until the meat is browned and the onion is soft. Drain off any excess grease, then stir in the minced garlic and cook for about 30 seconds, just until you can smell it. Garlic can go from fragrant to scorched quickly, so this is one of those moments when I stay near the stove instead of wandering off to deal with whatever mysterious noise just came from the living room. Pour in the marinara sauce, then add the Italian seasoning, salt, and black pepper. Stir everything together and let the sauce simmer for about 5 minutes. That short simmer gives the onion, garlic, beef, and tomato sauce time to settle into one another before you start layering.