Combine tomato puree, curry powder, garlic, salt, pepper, and 3 tblsp. oil. Rub the chicken outside and inside with this mixture and leave it for about 1 hour for the flavor to penetrate the meat. Grill or roast the chicken until nicely browned and tender (a spit is ideal). Serve with a sauce made by combining the tamarind juice with enough seasoning to give a pleasantly sharp sweet-sour flavor.