In a 12 to 14-inch saute pan, heat olive oil over medium heat and add garlic. Cook gently until softened and very light golden brown, then add tomatoes and cook, stirring, until tomatoes begin to break down. Add cauliflower and mix well. Stir in 1/2 cup very hot water, and simmer for 30 minutes, or until cauliflower is tender.
Bring 6 quarts of water to a boil and add 2 tablespoons salt. Add the penne, and cook according to package directions, until tender yet al dente.
Drain apenne and add to the pan with the cauliflower. Stir in parsley and black pepper, to taste, and toss 1 minute over high heat. Divide evenly among 6 warmed pasta bowls, top with grated cheese, and serve immediately.