Heat the olive oil in a large Dutch oven or soup pot over medium-high heat. Add the Italian sausage and cook for 5-7 minutes, breaking it into small pieces until browned; drain excess fat if necessary.

Add the diced onion and cook for 3-4 minutes until softened. Stir in the minced garlic and cook for about 30 seconds.

Stir in the tomato paste, Italian seasoning, and optional red pepper flakes. Cook for 1 minute so the tomato paste lightly caramelizes.

Add the tomatoes, broth, bay leaf, kosher salt, and black pepper. Bring the mixture to a boil.

Stir in the broken lasagna noodles. Reduce the heat to medium-low and simmer uncovered for approximately 10-15 minutes, stirring occasionally, until the noodles are tender.

Remove the bay leaf and taste the soup. Adjust the salt and black pepper, then ladle into bowls and top with ricotta, mozzarella, Parmesan, and fresh herbs.