Within the world of Cuban-style black beans there are many variations. The beans ought to be fresh and the seasonings tasty, but after that opinions diverge. What seasonings and in what combinations? Garlic, of course. But what about onions, green pepper, salt, pepper, cumin, even tomato sauce? This restaurant, a Little Havana fixture for 27 years, enjoys the talents of long-time chef Guillermo Martinez, who has found a formula that works. This includes garlic, green peppers, olive oil, and white sherry, according to restaurant manager Orestes Lleonart, Jr. Ah, but there's more. And that part is a secret. "The rest," says Lleonart, "is what only the cook knows." Dig into a bowl of black bean soup for $2.50.