Combine the salt, turmeric, cumin, black pepper, and garlic in a small bowl. Place the fish on a plate. Sprinkle the fish evenly on both sides with the spice mixture. Cover and marinate the fish for 20 minutes at room temperature or up to 4 hours in the refrigerator. Preheat oven to 400 degrees F. Lightly grease the bottom of a baking dish with the oil (use a large enough dish to fit the fish in a single layer). Place the fish in an even layer in the bottom of the baking dish. Bake at 400 degrees F, uncovered, for 20-25 minutes or until the fish flakes easily with a fork (actual cook time will depend on the thickness of the fish). Sprinkle the fish with the lemon juice just before serving. Serve hot.