Maybe the hardest thing to find in Washington is a good-plain broiled fish. So Kushner's is a find. Their broiled whole flounder is fresh and moist, heavily flavored with charcoal. And their "seafood in brochet" is a handsome platter of lobster tail, shrimp, scallops and fish filets sprinkled with paprika and broiled until just cooked through and still juicy, served on buttery rice. Fried seafoods are not so unequivocal; oysters and scallops turn out fine, but the crab cakes are heavy and the butterfly shrimp dry. The rest of the food compares unfavorably, from the large salads with a choice of bright orange or pink dressing, to the canned vegetables, to the thick crab soup with very little crab. The dill pickles placed on the table when you are seated turn out to be the best vegetable, and the rum buns make a good dessert. The restaurant has a certain historic appeal, being a perfect representation of a 1950s knotty pine rec room, with formica tables and yellow and black Naugahyde booths. Waitresses specialize in the gruff-exterior-with-a-heart-of-gold-style, and serve promptly. Take cash, for the restaurant accepts no credit cards or checks. And concentrate on the broiled fish.