Tamarind Shrimp Curry

Name: Tamarind Shrimp Curry
Ingredients: ¼ cup / 20 g coriander seeds; 1 pound / 450 g medium shrimp, peeled and deveined (28-32 pieces); 2 teaspoons turmeric powder, divided; 1½ teaspoons red chile powder or cayenne pepper, divided; 1 tablespoon plus ½, teaspoon plus 1 pinch salt, divided; 4 tablespoons / 60 mL coconut oil, divided; ½ teaspoon mustard seeds; 20 fresh curry leaves; 1 large yellow or red onion, finely diced; 1-2 fresh Thai, serrano, or cayenne chiles, stems removed and finely diced; 1 (2-inch / 5-cm) piece ginger, peeled and grated; 10 cloves garlic, peeled and minced or grated; 5 medium tomatoes, peeled and diced; 1 teaspoon tamarind paste; 1 tablespoon light brown sugar; 2 cups / 470 mL water; ¼ cup / 60 mL coconut milk (regular or light); Brown or white basmati rice, for serving