In a large pot of boiling salted water, cook the lasagna noodles according to package instructions until al dente. Drain and lay them out flat on a clean surface.
In a mixing bowl, combine ricotta cheese, 1 cup of mozzarella cheese, ½ cup of Parmesan cheese, egg, chopped spinach, Italian seasoning, salt, and pepper. Mix until well combined.
In a skillet over medium heat, cook the ground beef until browned. Add minced garlic and cook for another minute. Drain excess fat, then stir in marinara sauce and let it simmer for 5 minutes.
Spread a thin layer of the meat sauce in the bottom of a 9x13 inch baking dish.
Place 3 lasagna noodles over the sauce. Spread a layer of the ricotta mixture (about ⅓), then add another layer of meat sauce over the top. Repeat the layering process (noodles, ricotta, meat sauce) two more times until all ingredients are used, finishing with a layer of meat sauce.
Sprinkle the remaining mozzarella and Parmesan cheese on top of the last layer.
Cover the dish with aluminum foil (to prevent sticking, spray foil with cooking spray) and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15 minutes until the cheese is bubbly and golden.
Allow the lasagna to rest for 10-15 minutes before serving. Garnish with fresh basil leaves before slicing.
Notes
Slice the lasagna into squares and serve on individual plates. Drizzle with a little extra marinara sauce and top with additional basil for a pop of color.