Preheat the Bull Grill to medium-high heat. Trim away the leaves at the bottom of the cauliflower head. Cut off and remove as much of the stem and tough core as possible while leaving the head intact.
Rinse and pat dry the trimmed cauliflower head. Spray the cauliflower with avocado oil or duck fat until the cauliflower is well coated. Season both sides of the cauliflower liberally with salt & pepper.
Place the cauliflower florets-side up on a cast-iron skillet, and cover tightly with aluminum foil. Turn off the middle two burners of the Bull Grill. Place the cast iron over the area with indirect heat and cook for 20 minutes.
Remove the foil from the skillet, and pour lemon juice evenly over the cauliflower. Then sprinkle the crushed garlic and lemon zest all over the cauliflower.
Cook until the cauliflower is golden brown on the outside and fork-tender on the inside.
Remove from Bull Grill, cut into sections, and serve.
