Preheat the oven to 350 degrees F (175 degrees C).
STEP 2
Cook sausage in a skillet over medium heat until evenly browned. Drain grease. Add Alfredo sauce and spinach; season with pepper. Cook until heated through.
STEP 3
Combine Cheddar cheese, ricotta cheese, Parmesan cheese, and egg in a bowl.
STEP 4
Layer 1/3 sausage mixture, 1/3 noodles, and 1/3 Cheddar mixture in a 9x13-inch baking dish. Repeat layers twice; top with mozzarella cheese. Cover with aluminum foil.
STEP 5
Bake in the preheated oven for 45 minutes. Let stand 15 minutes before serving.