You have to be mighty confident to name your restaurant Triomphe, but indeed the team behind this jewel box in the Iroquois Hotel has triumphed. The dining room is pleasing but unfussy, and chef Steve Zobel's wide-ranging menu is ambitious yet understated. Appetizers usually include chicken livers with sherry and onions, and seared scallops with a light licking of truffle oil. Zobel's striped bass gets a ginger-chili marinade, and he serves a spoon-tender braised domestic lamb shank with root vegetables and saffron couscous. Desserts are simple but impeccable, especially the tarte tatin, which is caramelized to a fare-thee-well. Reservations essential. Subway: B, D, F, V to 47th-50th Sts.