Bring a large pot of salted water to a boil. Cook the pasta according to the package directions until al dente. Reserve about 1/2 cup of pasta water, then drain the pasta.
Heat the olive oil in a large skillet over medium heat.
Add the cherry tomatoes and cook for 4–5 minutes, stirring occasionally, until they begin to soften.
Add the minced garlic, tomato paste, and Italian seasoning. Cook for about 1 minute, stirring frequently.
Reduce the heat to medium-low and pour in the heavy cream. Stir until smooth and allow the sauce to gently simmer for 2–3 minutes.
Add the fresh spinach a handful at a time and stir until wilted.
Reduce the heat to low and stir in the Parmesan cheese until melted and incorporated into the sauce.
Add the cooked pasta and toss until evenly coated.
Add reserved pasta water a little at a time if needed to loosen the sauce.
Season with salt, black pepper, and optional crushed red pepper flakes.
Garnish with fresh basil or parsley and additional Parmesan cheese before serving.