Place fish fillets into a medium sized bowl and sprinkle with salt, turmeric, cumin, black pepper and garlic, tossing to coat well. Cover and marinate for 50 - 60 minutes in the refrigerator. Preheat oven to 400 degrees F. Coat the bottom of an 8 x 8 inch baking dish with the vegetable oil. Place the fish in a single layer inside the baking dish, and pour the marinade on top. Bake uncovered for 20-25 minutes. The fish should be firm to the touch. Fish is done when it easily flakes with a fork. Sprinkle with lemon juice 5 minutes before serving.