Beer-Marinated Flank Steak with Aji and Guacamole

Colombia may be the best kept barbecue secret in South America. Sure, Argentina gets the attention for its cowboy-style asado. And Brazil has enjoyed spectacular success exporting its rodizio-style restaurants—the kind where the waiters parade spits of grilled meats through the dining room. But Colombia? I doubt that most North Americans could name a single Colombian grilled dish. Well, it's time to shine the spotlight on the only country in South America to have coasts on both the Atlantic and the Pacific, whose cool-weather ranching district produces well-marbled, full-flavored beef, whose grill masters make extensive use of marinades (unlike the simplicity prized by their Argentine counterparts), and whose mastery of the art of grilling on charcoal extends to some unique techniques. Here's a not-so simple flank steak redolent of cumin, green onions, and beer.