Heat the olive oil in a large skillet over MEDIUM heat. Add the onion to the skillet, and cook, stirring often, until softened, about 2 to 3 minutes. Add the garlic and sauté for another minute or two.

Add the broth, diced tomatoes, tomato sauce, Italian seasoning, crushed red pepper flakes, salt, pepper, and the pasta. Increase heat and bring to a boil. Cover the skillet, reduce to LOW and simmer for 15 to 18 minutes, or until pasta is al dente.

Stir in the half and half or cream, half of the Parmesan, and the shrimp and cook over MEDIUM-LOW heat until the shrimp is opaque, slightly pink, and cooked through, about 3 to 4 minutes. Add the spinach in a big heap on top. You want spinach to still have some life to it so remove the skillet from the heat after you add it and stir it in just until it wilts. Sprinkle remaining Parmesan over the top, and serve.