Cook the pasta according to the package directions.
Pour 2 inches of water in a pot, insert a steamer basket, and bring the water to a boil over medium-high heat. Pile the cauliflower florets into the basket, cover the pot, and steam until the florets are crisp-tender, about 10 minutes.
In a large skillet, warm the olive oil over medium heat. Add the lemon juice, shallots, garlic, salt, and pepper, and sauté until the shallots are soft, about 3 - 4 minutes. Add the wine, and simmer until reduced by half, about 7 minutes.
When the cauliflower is done, lift the basket containing the florets and empty them into the skillet. Add the red pepper flakes, half of the parsley, and half of the Parmesan (if using). Sauté for another 2 - 3 minutes.
Scoop out ½ cup of pasta water, drain the pasta in a colander, and return the pasta to the pot over medium-low heat. Empty the skillet's contents into the pot with the pasta and toss with a wooden spoon.
Transfer the cauliflower scampi and pasta to a serving plate and top with the remaining parsley and Parmesan cheese (if using). Serve warm.