1. In a large saucepan, heat the oil over medium heat. Add the onion; cook, stirring, just until golden, about 7 minutes. Stir in the garlic and red-pepper flakes; cook for 1 minute.
2. Add tomatoes with their liquid and the salt. Stir in cauliflower and 1/2 cup water. Partially cover pan. Bring to a simmer; cook, stirring occasionally, 30 to 45 minutes or until cauliflower is very tender. (If mixture becomes too dry, add a little more water.) With back of wooden spoon, break up cauliflower into smaller pieces.Bread Crumb Topping:
3. Meanwhile, in small skillet, heat the olive oil. Add the garlic and bread crumbs; cook over medium heat, stirring often to coat the bread crumbs, until the crumbs are evenly toasted, about 3 minutes. Set aside.Pasta:
4. Meanwhile, in a large pot of lightly salted boiling water, cook the pasta following the package directions. Drain the pasta well.
5. Immediately in a large bowl, toss the hot pasta with the cauliflower sauce. Spoon onto warm serving dishes. Sprinkle with the bread crumb topping. Serve immediately. Makes 6 servings.