01 - Cook ziti in a pot of salted boiling water until al dente. In a separate pan, brown ground beef over medium-high heat. Drain excess fat. Stir in marinara sauce and simmer 2 minutes.
02 - Combine ricotta cheese and chopped spinach in a mixing bowl. Mix thoroughly until spinach is evenly distributed.
03 - In a baking dish, layer half the cooked pasta, followed by half the beef and marinara mixture, and half the ricotta-spinach mixture. Repeat layers. Top with shredded mozzarella cheese.
04 - Bake at 375°F for 30 minutes or until cheese is melted and golden. Let rest 5 minutes before serving.