Preheat the oven to 350 degrees F. Prepare a small casserole dish with non-stick spray.
In a steamer insert over boiling water, steam the cauliflower florets for 5 minutes, until crisp-tender. (You can also blanch the cauliflower in boiling water for 4-5 minutes.) Remove from heat, and drain if necessary to remove excess water.
Meanwhile, in a large mixing bowl, stir together the sour cream and cream cheese, until smooth. Stir in the shredded cheese, chopped bacon, green onion, salt, pepper, and garlic powder. Add the cauliflower florets to the bowl and mix with the sauce.
Pour the cauliflower mixture into the casserole dish. Bake for 15-20 minutes, until the cheese melts and the sauce is bubbly.