Heat oil: Heat the oil in the skillet medium heat.
Cook the sausage: Remove the sausage from the casing and add to the pan. Use your wooden spoon to break up the sausage and stir it.
Cook almost all the way through: Cook until the sausage gets a little color and is no longer pink and remove with a slotted spoon to a plate.
Add onions and garlic: Leave all but 1 tablespoon of the fat. Add in the onions and begin to cook for 1-2 minutes. Add in the garlic. Cook until the onion is translucent, about 5 minutes.
Add tomatoes: Stir in the tomatoes and season with salt and pepper. If you like it spicy, add in some crushed red pepper. Let simmer for 10 minutes, stirring occasionally while it simmers.
Add the cream: Add in the cream and stir to combine.
Add sausage: Stir back in the sausage and let simmer a few minutes.
Let simmer: Stir back in the sausage and let simmer a few minutes.
Cook pasta: Bring a large pot of salted water to boil. While the sauce is cooking, cook the pasta until it's al dente (look at the cooking time on your pasta box/bag) and set a timer to remind yourself.
Add spinach: When the pasta is almost ready, stir in the spinach. It takes only a minute to cook up.
Combine pasta with the sauce: Reserve a ¼ cup of the starchy pasta water. Drain the pasta and toss with the sauce in the skillet on medium heat. If needed, add a bit of the starchy pasta water and stir to combine.
Plate up and serve: Serve with grated Parmigiano cheese and hot pepper flakes, if you like. ENJOY! Buon appetito!