01 -
Preheat the oven to 375°F. Pour the water into a deep baking dish or oven-safe skillet.
02 -
Pull off the outer leaves and slice the very bottom of the stem so the head sits flat. Cut a shallow cross into the base of the stem to help the center cook evenly. Pat the cauliflower completely dry.
03 -
Melt the butter and stir in the garlic, lemon zest, salt, black pepper, and red pepper flakes if using.
04 -
Place the cauliflower stem-down in the dish. Brush about half the garlic butter all over the top and sides. Roast uncovered for 30 minutes.
05 -
Remove the pan and brush the remaining garlic butter over any pale spots. Return to the oven and roast another 25 to 35 minutes, until a paring knife slides easily into the center.
06 -
Let the cauliflower rest for 5 minutes, then slice into wedges or break into florets. Scatter fresh parsley over the top and serve.