Preheat your oven to 375°F (190°C) and gather your ingredients.

In a large skillet over medium heat, add your lean ground beef, chopped onion, and minced garlic. Cook for 8-10 minutes until browned.

Stir in marinara sauce and season with salt, pepper, and optional crushed red pepper flakes. Simmer for 10 minutes.

In a separate bowl, combine the ricotta cheese, egg, fresh parsley, and a pinch of salt and pepper. Mix until smooth.

In a 9x13-inch baking dish, layer ingredients: start with meat sauce, lasagna noodles, ricotta mixture, meat sauce, and sprinkle mozzarella.

Repeat the layering process and top with remaining meat sauce, mozzarella, and Parmesan cheese.

Cover with foil and bake for 25 minutes, then remove foil and bake for an additional 15 minutes until golden.

Let it rest for 10-15 minutes before serving.