Bring a large pot of water to a boil. Add salt and pasta and cook to al dente. Drain and reserve 2 ladles of pasta water.
While water is coming up to a boil and pasta cooks, make sauce. Heat a deep skillet over medium heat with extra-virgin olive oil. Add garlic and cook 3 minutes, then remove. Add onions and cook 5 minutes then add cauliflower, chicken stock and the rosemary. Cover the pan and cook 15 minutes. Uncover the sauce, add 1 to 2 ladles of pasta water and mash the cauliflower with the back of a wooden spoon or potato masher. Add the pasta and cheese to the cauliflower and toss to combine. Season the dish with salt and pepper, to taste, and serve.
Recipe courtesy of Rachael Ray