Flank steak, a flavorful yet affordable cut of beef, gets a salty-sweet boost from Michael Ruhlman's wonderful marinade. It also gives the meat a nice charred flavor, with or without an outdoor grill: as the marinade caramelizes, it creates aromatic smoke that infuses the meat, right in the hot pan. (Note: Allow 8 hours to fully marinate the steak.)
Marinade: Into a zip-top bag, add ketchup, soy sauce, brown sugar, onion powder, ground ginger, and Worcestershire sauce. Trim away the root end of garlic cloves, smash with the flat side of a knife, and discard the peel. Smash again, then roughly chop and add to the bag. Close the bag and mix the marinade. Makes about 1¼ cups. (Marinade will keep for up to 1 week in the refrigerator and up to 1 month in the freezer.)
Steak: Place steak into the bag with the marinade. Press out as much air as possible, seal the bag, and distribute the marinade around the meat. Let marinate for at least 1 hour at room temperature or, optimally, up to 8 hours to overnight in the refrigerator. (Note: If grilling after 1 hour of marinating, reserve the marinade to baste the steak during grilling.)
If the steak has been marinating in the refrigerator, bring it to room temperature before grilling, about 1 hour.Preheat grill pan (or outdoor grill) to medium-high heat. When grill pan is smoking hot, remove steak from marinade and lay it flat on the grill. Let cook for 4–5 minutes, largely undisturbed, pressing down on the meat to enhance grill marks if you wish. After 4–5 minutes, the steak should be lightly charred and no longer adhere to the grill. Lift and rotate steak about 60 degrees to create cross-hatched grill marks; let cook another 2–3 minutes. Finally, flip and repeat process on the other side, 7–8 minutes. (Total grilling time will be 15–16 minutes.)
After 15–16 minutes, steak should be medium-rare. Meat should feel firm to the touch at the thickest part (alternatively, a meat thermometer should register 125 F at the thickest part of the steak). Transfer steak to a wire rack fitted over a rimmed baking sheet. Let rest to allow the juices to redistribute in the steak, 15 minutes.
After the steak has rested, transfer to a cutting board. Find the grain of the meat, then thinly slice against the grain on a bias. Garnish with cherry tomatoes and greens, and serve immediately.