Heat the oil in a large Dutch oven over medium-high heat. Add the sausage and cook, breaking it up, until well browned, about 7 minutes. Leave the fat in the pot.

Add the onion and cook for 4 minutes until soft. Add the garlic, tomato paste, oregano, basil and pepper flakes and stir for 2 minutes, until the tomato paste turns a shade darker and starts sticking to the pot.

Pour in the crushed tomatoes and broth and scrape up the browned bits. Add the Parmesan rind, bring to a boil, then simmer uncovered for 10 minutes.

Add the broken noodles and simmer, stirring often so they don't stick, for 10 to 12 minutes, until tender. Stir in the spinach at the end until wilted. Remove the rind and season with salt and pepper.

While the soup simmers, mix the ricotta, mozzarella and Parmesan in a bowl with a pinch of salt and pepper.

Ladle the soup into bowls and top each one with a big spoonful of the cheese mixture and some basil. Serve right away.