Meat should be at room temperature. Remove all skin and fat. Use a sharp knife to slash chicken pieces in several pieces (cut through to the bone). Mix vinegar with salt and lemon juice. Coat the chicken with the vinegar mixture. Make a paste of ginger, onions and garlic in a mortar or food processor. Combine yogurt with onion paste, red pepper, garam masala and black pepper. Stir well to combine and add chicken. Cover and marinate at least 1 day, try 2 days. Let the chicken come to room temperature before grilling or baking at 180ºC . for 40 minutes. Use melted margarine to drizzle over chicken as it cooks. Serve on a bed of rice. The marinade can be used again.