Preheat oven to 450ûF.
Put a pot of water on to boil for pasta.
In a large bowl, combine cauliflower, tomatoes, garlic and oil. Toss to coat; spread out on a rimmed baking sheet. Roast, stirring once, until tender and slightly charred, about 20 minutes.
Meantime, boil pasta according to package directions. Reserving a mugful of the cooking water, drain pasta and return to pot. Add cauliflower mixture plus Parmesan, parsley, lemon juice and zest, and half the reserved pasta water. Toss to coat. For a thinner sauce, add more of the pasta water. Sprinkle with a little more cheese, if desired, and serve.
Per serving: 407 calories, 17 g protein, 7 g fat (1 g saturated fat), 75 g carbohydrates, 4 g fibre, 3 mg cholesterol, 120 mg sodium.