Preheat your oven to 350°F (175°C).
In a medium-sized saucepan, bring about 2 inches of water to a boil. Add the cauliflower florets and cover the pot, cooking for approximately 10 minutes, or until the cauliflower is tender. Once done, drain the cauliflower well and transfer it to a 2-quart casserole dish.
In a small bowl, combine the melted butter, grated Parmesan cheese, Italian bread crumbs, salt, and crushed red pepper flakes. Mix everything thoroughly, then evenly sprinkle this mixture over the cauliflower. Top it off with a generous amount of shredded Cheddar cheese.
Place the casserole in the preheated oven and bake for 20 minutes, or until the cheese has melted and is bubbling. Serve hot and enjoy!