This light, spicy soup is delicious hot or chilled. The sautéed aromatics turn the broth a rich red-orange, more reminiscent of tomato than watermelon. See if your guests can guess the main ingredient.

　　Active time: 1 hr Start to finish: 1 hr (3 hr if serving chilled)

　　

Ingredients

Makes 4 first-course servings

　　

For soup

5 cups coarsely chopped seeded watermelon (from a 4-lb piece, rind discarded)

　　1 fresh lemongrass stalk*

　　3 tablespoons finely chopped shallot

　　1 1/2 tablespoons finely chopped peeled fresh ginger

　　1 tablespoon finely chopped garlic

　　1 1/2 tablespoons mild olive oil

　　1 small hot green chile such as Thai or serrano, finely chopped (including seeds), or to taste

　　2 tablespoons fresh lime juice, or to taste

　　3/4 teaspoon salt, or to taste

　　

For crab

10 oz jumbo lump crabmeat (2 cups), picked over

　　1/4 cup finely chopped fresh cilantro

　　1 1/2 tablespoons mild olive oil

　　1/4 teaspoon salt, or to taste

　　Accompaniment: lime wedges

　　

Make soup:

Step 1

Purée watermelon in a blender until smooth and transfer to a bowl. (Don't wash blender.)

　　

Step 2

Discard 1 or 2 outer leaves of lemongrass and trim root end. Thinly slice lower 5 to 6 inches of stalk and then mince, discarding remainder.

　　

Step 3

Cook lemongrass, shallot, ginger, and garlic in oil in a 2-quart heavy saucepan over moderately low heat, stirring, until aromatics are pale golden, about 5 minutes. Add about one third of watermelon purée and simmer over moderate heat, stirring, 5 minutes.

　　

Step 4

Remove watermelon mixture from heat, then transfer to blender along with chile, lime juice, and salt and blend until smooth (use caution when blending hot liquids).

　　

Step 5

Add remaining watermelon purée and blend briefly. Season soup with more chile, lime juice, and salt if desired, blending if necessary. Pour soup through a sieve into a bowl, pressing on and then discarding any solids. Chill soup, uncovered, about 2 hours if serving cold, or reheat in cleaned saucepan.

　　

Prepare crab:

Step 6

Toss crabmeat with cilantro, oil, and salt.

　　

Step 7

Divide crab among 4 soup plates, mounding in center, and pour chilled or hot soup around it.

　　Cooks' notes:

　　• Soup can be made 1 day ahead and chilled. Cover after 2 hours of chilling. • Crabmeat can be picked over 1 day ahead and crab mixture can be prepared 1 hour before serving. Chill, covered. *Available at Asian markets and some supermarkets.