Japanese-style Bistek

"Bistek" is Tagalog for beef steak, and in our house we cook it usually with soy sauce and calamansi. Yesterday, I thawed our tenderloin steak from last Christmas and simmered it in hon mirin, Kikkoman soy sauce, three tablespoons of vinegar, lots of freshly ground pepper, and four thinly sliced, sauteed onions, for an hour. It was really good: very mild flavors, with a hint of sweetness, and the peppery feeling in the tongue I've always wanted in my grilled steak.