Step 1: Heat olive oil in a large pot or Dutch oven over medium heat. Add ground beef and onion, breaking up the beef with a spoon. Cook until beef is browned and onion is softened, about 8-10 minutes. Drain any excess fat.
Step 2: Stir in minced garlic and cook for 1 minute until fragrant. Add crushed tomatoes, tomato paste, water (or broth), oregano, basil, salt, and pepper. Bring to a simmer, then reduce heat to low, cover, and let it simmer for at least 20 minutes (or up to 1 hour for deeper flavor), stirring occasionally.
Step 3: While the sauce simmers, prepare the ricotta mixture. In a medium bowl, combine ricotta cheese, egg, 1/2 cup Parmesan cheese, chopped parsley, and optional nutmeg. Mix until well combined.
Step 4: Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Step 5: Spread about 1 cup of meat sauce on the bottom of the prepared baking dish. Arrange 3-4 lasagna noodles over the sauce, slightly overlapping if necessary. You may need to break some noodles to fit.
Step 6: Spread half of the ricotta mixture evenly over the noodles. Top with about 1.5 cups of shredded mozzarella cheese.
Step 7: Spoon another 1.5 cups of meat sauce over the mozzarella. Repeat the noodle, ricotta, mozzarella, and sauce layers once more.
Step 8: Place the final layer of 3-4 noodles on top. Cover with the remaining meat sauce and then sprinkle generously with the remaining mozzarella cheese and extra Parmesan.
Step 9: Cover the baking dish tightly with aluminum foil. Bake for 30 minutes. Remove the foil and bake for an additional 20-25 minutes, or until the cheese is bubbly and lightly golden brown. If desired, you can broil for the last 2-3 minutes for an extra golden crust, watching carefully to prevent burning.
Step 10: Let the lasagna rest for 10-15 minutes before slicing and serving. This allows the layers to set, making it easier to cut and serve neatly. Enjoy your delicious Easy Homemade Lasagna!