Step 1

FOR THE TAHINI-YOGURT SAUCE: Whisk all ingredients in bowl until ­combined. Adjust consistency with extra water as needed and season with salt and pepper to taste. (Sauce can be refrigerated for up to 2 days.)

Step 2

FOR THE CAULIFLOWER: Trim stem of cauliflower, keeping leaves intact, so it sits flat. Dissolve salt and sugar in 2 quarts cold water in large bowl. Holding cauliflower upside down by stem, gently dunk in brine and let sit for 5 minutes. Flip and continue to submerge for 1 minute until evenly moistened (do not pat dry). Transfer cauliflower stem down to large plate and cover with inverted large bowl. Microwave until cauliflower is trans­lucent and tender and paring knife inserted in thickest stem of florets (not into core) meets no resistance, 8 to 14 minutes.

Step 3

Carefully transfer cauliflower to paper towel–lined plate and pat dry. Whisk oil, turmeric, and pepper together in small bowl, then brush cauliflower with oil mixture.

Step 4

FOR A CHARCOAL GRILL: Open bottom vent completely. Light large ­chimney starter filled with charcoal briquettes (6 quarts). When top coals are partially covered with ash, pour evenly over half of grill. Set cooking grate in place, cover, and open lid vent completely. Heat grill until hot, about 5 minutes.

Step 5

FOR A GAS GRILL: Turn all burners to high; cover; and heat grill until hot, about 15 minutes. Leave primary burner on high and turn off other burner(s). (Adjust ­primary burner as needed to maintain grill temperature of 350 to 400 degrees; if using 3-burner grill, adjust ­primary burner and second burner.)

Step 6

Place cauliflower stem side down on cooler side of grill (6 to 8 inches from heat source for gas grill). Cover and cook until cauliflower is deeply browned and leaves are charred and crisp, 35 to 55 minutes, rotating ­cauliflower halfway through cooking. Using spatula and tongs, transfer ­cauliflower to plate.

Step 7

Spread two-thirds of tahini-yogurt sauce over ­serving platter. Center cauliflower stem side down on sauce and sprinkle with pistachios and parsley. Cut into wedges and serve, passing remaining sauce separately.