
Heat the olive oil in a large pot or Dutch oven over medium-high heat. Add the Italian sausage, if using, and cook for 5 to 9 minutes, breaking it into small pieces, until browned and cooked through. If there is a lot of grease, spoon off the excess and leave about 2 tablespoons in the pot.


Reduce the heat to medium. Add the diced onion, paprika, fennel seeds, 1 1/2 teaspoons salt, 1 1/2 teaspoons black pepper, and the crushed red pepper flakes. Cook, stirring often, for about 5 minutes, until the onion softens and the spices smell fragrant.

Stir in the tomato paste and minced garlic. Cook for 2 to 3 minutes, stirring constantly, until the tomato paste deepens in color. Pour in the crushed tomatoes and stock, raise the heat to medium-high, and bring the soup to a gentle boil.



Add the tortellini and cook until tender according to the package timing, about 3 minutes for refrigerated tortellini or 4 minutes for frozen. Stir occasionally so the pasta does not stick to the bottom of the pot.


Lower the heat and stir in the heavy cream, chopped kale, and basil. Cook for 2 minutes, just until the kale wilts and everything is heated through. Remove from the heat, stir in the lemon juice, and taste before adjusting with more salt and black pepper if needed.

Ladle the soup into bowls and finish with plenty of grated Parmesan before serving.