Bring a large pot of water to a boil. Cook the bow tie pasta according to package directions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium-high heat. Add the Italian sausage and red pepper flakes (if using). Cook, breaking up the sausage with a spoon, until browned and cooked through.
Add diced onion and minced garlic to the skillet. Cook until the onion is tender and translucent.
Stir in the chopped tomatoes and heavy cream. Simmer the sauce until it thickens slightly, about 10 minutes.
Add the spinach strips to the skillet and cook for an additional 3 minutes, until wilted.
Add the cooked pasta to the sauce and toss until evenly coated.
Garnish with minced fresh parsley, if desired, before serving.
Serve hot and enjoy this delicious Italian Sausage Bow Tie Pasta with your favorite crusty bread or a side salad.