How to Make It
Preheat the oven to 450°. On a large rimmed baking sheet, toss the cauliflower with the olive oil and season with salt and pepper. Roast for 40 minutes, or until tender and browned; let cool.
Meanwhile, in a large skillet, working in 2 batches, cook the bacon over moderate heat until crisp, about 4 minutes per side. Drain on paper towels, then coarsely chop the bacon.
Butter 2 large shallow baking dishes. In a large pot of boiling salted water, cook the penne just until al dente; drain. Return the penne to the pot. Stir in the cauliflower, tomatoes, cream, garlic, thyme, crushed red pepper, 2 cups of the Fontina cheese and 3/4 cup of the Parmesan; season with salt and pepper. Transfer the pasta to the prepared baking dishes and sprinkle with the remaining 1/2 cup of Fontina and 2 tablespoons of Parmesan. Bake for 15 minutes, or until bubbling and lightly browned. Sprinkle the pasta with the parsley and chopped bacon and serve.