Place rice, water and ½ tsp salt in a saucepan. Bring to a boil, cover and simmer 15 minutes, until rice is tender and water is absorbed. Cook ginger, spices and garlic in butter until fragrant, 1-2 minutes. Add onion and tomato and cook 3-4 minutes. Stir in rice, tuna and cilantro and heat through. Serve with lemon wedges. Serves 4.