Preheat oven to 375 degrees. Lightly grease a baking dish then set aside.
In a small bowl, mix together the mayonaise, parmesan cheese, garlic powder, salt and pepper until combined.
On the stove, bring a large pot of water to boil. Add the cauliflower head and cook for approximately four minutes. (Two minutes each side)
Remove the cauliflower from the pot, pat the cauliflower dry, then place the cauliflower in the baking dish. Spread the mayonaise cheese mixture evenly over the cauliflower.
Bake at 375 degrees for approximately 20 minutes. Remove from oven, slice and serve.