Gather all ingredients, chop the onion, and mince the garlic to prepare for cooking.
Heat the large heavy-bottomed pot over medium heat, adding a splash of olive oil until shimmering and fragrant.
Add the Italian sausage to the pot, breaking it apart with a wooden spoon as it cooks, until browned and cooked through, about 7 minutes. The sausage should emit a rich aroma and develop a deep color.
Stir in the chopped onion and minced garlic, cooking until fragrant and translucent, about 5 minutes. You'll notice the onion turning soft and slightly golden.
Pour in the crushed tomatoes along with the beef broth, stirring to combine. Bring the mixture to a gentle simmer, watching for bubbling around the edges.
Add the broken lasagna noodles to the simmering broth, stirring gently. Cook until the noodles are just tender, about 10 minutes, stirring occasionally to prevent sticking.
Sprinkle the shredded mozzarella and grated Parmesan cheeses over the hot soup, allowing them to melt into a bubbly, cheesy layer that coats the surface beautifully.
Once the cheese has melted and the soup is hot and bubbling, ladle it into bowls and garnish with chopped fresh basil or parsley for a bright, herbal finish.
Serve the soup immediately, enjoying the thick, cheesy texture and vibrant tomato flavors in every hearty spoonful.
