Recipe from Martha Stewart.com
4 small flat-iron steaks (each about 6 ounces and 1 inch thick)
Coarse salt and ground pepper
1 cup dry red wine, such as Merlot or Cabernet Sauvignon
2 tablespoons cold butter, cut into pieces
Heat a large cast-iron or other heavy-bottomed skillet over medium-high until very hot. Season steaks with salt and pepper. Add to skillet; sear 4 to 8 minutes per side for medium-rare (if browning too quickly, reduce heat after turning steaks). Transfer steaks to a plate, and cover loosely with aluminum foil (reserve skillet).
Add wine to skillet; simmer over medium-high, stirring occasionally and scraping up browned bits with a wooden spoon, until syrupy, 4 to 6 minutes. Remove skillet from heat. Stirring constantly, drop butter into sauce, one piece at a time, waiting for each piece to blend in before adding the next. Season with salt and pepper. Serve steaks drizzled with sauce.