Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente, drain and transfer to a large bowl.
While pasta water is coming to boil, rinse and slice tomatoes in half. Heat olive oil in a 12" skillet over medium heat. Add tomatoes, then garlic, pepper, salt, and crushed red pepper. Cook, stirring occasionally, until half of the tomatoes begin to burst and release their juices, 4-5 minutes. Use reserved pasta water to thin the sauce to the desired consistency.
Toss pasta with tomato sauce and spinach. Top with Parmesan Cheese.