Sometimes I get a low-down and dirty craving for liver and onions, and nothing else will do. Since the aroma of frying liver offends the delicate sensibilities of my family, I sneak out alone to satisfy my shameful urge at the nearest Luby's Cafeteria (5215 Buffalo Speedway, 664-4852, and other locations around Houston). Luby's dishes up a generous quarter-pound of thinly sliced beef liver, dredged in egg wash and breaded with finely ground breadcrumbs, then grilled and topped with soft, golden sauteed onions ($3.25). The breading and quick grilling make the fork-tender difference. And I'm not the only one who thinks it's the best plate of liver and onions in Texas. "It's one of our most requested recipes," says Stacy Jackson, a spokesperson for Luby's Corporation. "Even people who don't like liver like Luby's liver."