In a microwave-safe bowl, add onions, carrots, and red bell peppers. Cook in microwave for 3 minutes, to soften.
Heat olive oil in a large, nonstick pot. Add softened vegetables and garlic. Cook and stir over medium heat for 1½ minutes. Add sausage pieces and continue to cook, stirring often, for 2 minutes. Stir in broth, crushed tomatoes, and pizza or pasta sauce. Add Italian seasoning, red pepper flakes, and black pepper. Bring to a boil.
Stir in tortellini and kale. Turn heat to medium-low. Cover, and simmer for 8 minutes, until pasta is tender (al dente) but not overcooked. Stir often.
Ladle into bowls. Top each with a little Parmesan cheese, if desired.
Since the pasta absorbs some of the liquid when reheating, you might need to add a little more chicken broth or water.
This soup freezes great, too.