Some people will direct you to 6th Street in the East Village for Indian food. Don't go. Instead, follow the off-duty cabs to the real locus of authentic regional Indian cooking, which radiates from the intersection of 28th Street and Lexington Avenue. There you will find Pongal, an attractive, narrow restaurant with a cow in the window. Fragrant (and kosher) vegetarian southern Indian food issues forth from the kitchen. Start with one of the combination platters (thalis), on the back of the overwhelming menu. The Gujarati thali comes with a selection of southern specialties, including a vegetable stew with eggplant and lotus root, seasoned yogurt, fragrant basmati rice, steamed, lentil cake, and other treats.