Step 1

Preheat oven to 425°F.

Step 2

Place whole cauliflower in a metal pie pan. Drizzle with oil and sprinkle with salt and pepper. Pour water around the cauliflower and cover the pan tightly with foil. Bake until a knife is easily inserted into the center, 40 to 50 minutes. Remove from oven. Preheat broiler to high.

Step 3

Meanwhile, combine mozzarella and pesto in a small bowl. When the cauliflower is cool enough to handle, separate areas between the florets and fill with the pesto mixture. Save a little of the mixture and spread it on top of the cauliflower. Return to the oven and broil until melted and golden on top, 4 to 5 minutes.