Preheat oven to 425° Fahrenheit. Spray a 9x13-inch baking dish with non-stick spray.
Cut the cauliflower into bite-size florets. Place the cauliflower in a medium-size pot and fill the pot with 1-inch of water. Steam for 5-7 minutes. The cauliflower should be tender but still have a crunch. Drain the cooked cauliflower.
Combine sour cream, cream cheese, 3 cups Cheddar cheese, onion powder, and garlic powder in a large mixing bowl.
Fold in the cauliflower and chopped bacon (from the 6 slices).
Pour the cauliflower mixture into the prepared baking dish and bake for 25 - 30 minutes uncovered.
Remove the casserole from the oven and sprinkle the remaining cheese and chopped bacon. Bake for an additional 5 minutes.
Remove from oven and let cool for 5 minutes before serving. Sprinkle with chopped green onions, if desired.
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Notes
Feel free to add chopped green onions to the mixture prior to baking for additional flavor.Other cheeses work well in this recipe, too, such as Pepper Jack, Monterey Jack, and Swiss.