This simple stir-together relish gets umami from soy sauce, brightness from lemon juice and fragrance from fennel and cumin seeds. To crush the seeds, use a mortar and pestle or the bottom of a heavy skillet; alternatively, pulse them a few times in a spice grinder. Whatever your method, leave them with some texture—don’t pulverize them to a powder. If using flank or skirt steak, cut the meat into two or three pieces that fit comfortably in the skillet.