Step 1Pour the peanut oil into a medium bowl. Add the salmon and turn to coat. Set fish aside for 30 minutes.
Step 2Soak 16 bamboo skewers in water for at least 30 minutes. Prepare a medium-hot grill fire.
Step 3While the salmon is marinating in the peanut oil, heat the olive oil in a large saute pan over medium heat. Add the onion and garlic, and saute until the onion is translucent, about 5 minutes. Stir in the curry powder, vinegar, red wine, cornstarch, tamarind and sugar. Bring to a simmer. Reduce the heat to low, and simmer for 5 minutes, or until the sauce thickens slightly. Remove the sauce from the heat and let it cool slightly.
Step 4Transfer the sauce to a blender and puree until smooth; this makes 2 cups. Place 1 cup in a small serving bowl and set aside. Reserve the remaining sauce for basting the salmon.
Step 5Sprinkle the salmon with the salt and thread it onto skewers. Arrange the skewers on the grill and cook for 3 to 4 minutes on each side, or just until cooked through, brushing frequently with the tamarind sauce.
Step 6Serve with the bowl of reserved sauce.