It's the kind of mouthwatering soup that would make Seinfeld's Soup Nazi (admit it, you watch the reruns) jealous with rage. Only it's prepared by a soft-spoken, gentle mom (Christine Vouras), using family recipes that she once served at one of Dallas' swankiest restaurants, Chateaubriand (1958-1982). Her only problem is selecting two soups a day from among her 21 recipes to meet the desires of the regulars at the Metropolitan Café, an urban outpost along downtown's edge, next to the old municipal courthouse. Whether it's a hot winter broth, such as lentil or chicken gumbo, or a cool summer soup, such as cucumber or gazpacho, the ingredients are fresh, tasty, natural and healthful, a frothy alternative for those who wish to drink their lunch and stay sober.