01 - In a large, deep skillet over medium heat, cook the ground beef or sausage until browned, breaking it up with a spoon. Drain excess fat if needed.
02 - Add the diced onion and cook for 3–4 minutes until softened. Stir in garlic and cook for 1 minute until fragrant.
03 - Add crushed tomatoes, tomato paste, oregano, basil, red pepper flakes if using, salt, and black pepper. Stir well to combine all ingredients.
04 - Add the broken lasagna noodles, submerging them in the sauce. Add 1/2 cup of water if the sauce seems too thick to coat the noodles.
05 - Cover and simmer over medium-low heat for 15–18 minutes, stirring occasionally, until noodles are tender and sauce has thickened.
06 - Dollop ricotta cheese evenly over the lasagna, then sprinkle with mozzarella and Parmesan cheeses.
07 - Cover and cook for another 3–5 minutes, until the cheese is melted and bubbly throughout.
08 - Remove from heat and let sit uncovered for 5 minutes to set. Garnish with fresh basil or parsley if desired. Serve warm.