Ingredients

• 1 teaspoon coriander seeds
• 1/2 teaspoon cumin seeds
• 1 (1-inch) piece cinnamon stick, broken into pieces
• 4 whole cloves
• 1/4 cup unsweetened dried grated coconut
• 1 teaspoon hot red-pepper flakes
• 1/2 teaspoon turmeric
• 3 tablespoons vegetable oil
• 1 medium onion, finely chopped
• 3 garlic cloves, finely chopped
• 1 tablespoon grated peeled ginger (use a Microplane)
• 2 (4-inch) fresh hot green chiles, cut lengthwise into thin shreds, plus seeds
• 1/4 cup Swad-brand tamarind concentrate (see cooks' note, below)
• 1 cup finely chopped plum tomato (1 large)
• 1 1/2 lb large shrimp, peeled
• 1 teaspoon coarse sea salt such as fleur de sel
• 2 teaspoons Sherry vinegar or red-wine vinegar
• Equipment: an electric coffee/spice grinder
• Accompaniment: basmati rice or Indian bread

Instructions

1. Toast coriander, cumin, cinnamon, and cloves in a small heavy skillet over medium heat, shaking skillet, until fragrant and darker (do not burn), 3 to 4 minutes. Stir in coconut, red-pepper flakes, and turmeric and cook, stirring, until coconut is golden brown, 1 to 2 minutes. Transfer to a bowl and cool completely, then pulse in grinder until finely ground.
2. Heat oil in a 12-inch heavy skillet over medium-high heat until it shimmers, then sauté onion until golden, 3 to 5 minutes. Add garlic, ginger, chiles, tamarind, and spice mixture and cook, stirring, 30 seconds. Add tomato and cook, stirring, until sauce is thickened, 3 to 4 minutes.
3. Toss shrimp with sea salt, then add to sauce and cook, stirring, until just cooked through, 3 to 5 minutes. Stir in vinegar and season with sea salt.