Ingredients

• 1 cup dry crab boil seasoning (such as Zatarain's or Old Bay)
• 1/4 cup kosher salt
• 2 yellow onions, quartered
• 6 garlic cloves
• 3 lemons, halved crosswise
• 2 1-pounds heads of cauliflower, cored, trimmed into 2" florets
• Cocktail sauce
• Ingredient info: Crab boil seasoning is available at most supermarkets in the seafood or spice section, and at specialty foods stores.

Instructions

1. Combine crab boil, salt, onions, garlic, and 6 quarts water in a large pot. Squeeze juice from lemons into pot and add lemon halves. Set pot over high heat and bring liquid to a boil. Cook for 10 minutes to let flavors meld. Using a slotted spoon, remove onions, garlic, and lemons from broth; discard. Return liquid to a rolling boil.
2. Add cauliflower; turn off heat, cover pot tightly, and let stand until cauliflower is crisp-tender, 5-10 minutes. Drain; spread out cauliflower on a rimmed baking sheet and let cool completely. DO AHEAD: Cauliflower can be made 1 day ahead. Cover and refrigerate.
3. Arrange room-temperature or chilled cauliflower on a platter with cocktail sauce for dipping.