In a large pot of salted boiling water, cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large skillet over medium heat, add olive oil. Once hot, add the Italian sausage. Break it apart with a spatula and cook until browned and cooked through, about 5–7 minutes.
Add the chopped onion and minced garlic to the skillet with the sausage. Sauté until the onion is translucent and fragrant, about 3–4 minutes.
Pour in the chicken broth and heavy cream. Stir well to combine. Then, add the Italian seasoning, red pepper flakes (if using), salt, and pepper.
Bring the mixture to a gentle simmer. Add the chopped spinach and halved cherry tomatoes, stirring until the spinach is wilted, about 2–3 minutes.
Add the cooked penne pasta to the skillet and toss everything together until the pasta is well-coated with the sauce.
Taste and adjust the seasoning with more salt and pepper if needed.
Plate the pasta into bowls, then garnish with fresh basil and a generous sprinkle of grated Parmesan cheese.
Notes
Feel free to adjust the spice level by adding more or less red pepper flakes.