
Meanwhile, heat olive oil in a large, deep non-stick skillet. Add garlic and hot pepper flakes and cook gently for a few minutes but do not brown. Add tomatoes to skillet. Bring to boil. Reduce heat and cook for 5 minutes. Add spinach and cook just until it wilts.
Bring a large pot of water to boil. Add penne and cook until tender but firm. Drain well and add to skillet with sauce. Toss gently over low heat until everything is hot and sauce clings to noodles. Taste and season with salt and pepper.