Cook the beef – In a skillet over medium heat, cook ground beef and onion until browned. Drain excess grease, then stir in minced garlic and cook for 1 more minute. Add to slow cooker – Transfer the beef mixture to the crockpot. Add crushed tomatoes, diced tomatoes, beef broth, tomato paste, Italian seasoning, salt, black pepper, and red pepper flakes. Stir to combine. Slow cook – Cover and cook on low for 6-8 hours or high for 3-4 hours. Add pasta – About 30 minutes before serving, add broken lasagna noodles and stir. Cook until pasta is tender. Prepare ricotta topping – In a small bowl, mix ricotta cheese, parsley, and salt. Finish the soup – Stir in shredded mozzarella and Parmesan until melted. Serve & enjoy – Ladle soup into bowls, top with a scoop of ricotta mixture, and enjoy!