Using a mortar and pestle, make a paste of the garlic, ginger, ¼ teaspoon turmeric, salt, cilantro,chili 1 ½ tablespoons water; set aside.
Soak the dried lime for a few minutes in water to soften the skin.
Make a small hole by piercing it with a paring knife or fork.
Bring 5 cups water to a boil in a medium saucepan over medium-high heat
Add the black pepper and the remaining ½ teaspoon turmeric and cook 2 minutes.
Add the tomato, boil 5 minutes, then add the onion, and cook 5 minutes more.
Stir in the lime juice, garlic-ginger paste, cayenne, and dried lime; cover, decrease the heat to medium-low, and cook 15 minutes.
Remove the dried lime
Add the tuna and gently stir, cover and simmer until the fish is cooked through,
Serve over cooked basmati rice
Garnish with chopped cilantro and lime wedges.