Step 1

Stir ¼ cup distilled white vinegar, 3 Tbsp. sugar, 2 Tbsp. fish sauce, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a small bowl until sugar is dissolved. Add 2 small Persian cucumbers, halved lengthwise, sliced ½" thick, 2 small shallots, halved, thinly sliced, 4 garlic cloves, finely chopped, 2 red Thai chiles or 1 serrano chile, thinly sliced, and zest of 1 lime; mix to combine. Let sit at least 15 minutes and up to 1 hour (makes about 2 cups).

Step 2

Stir 2 Tbsp. vegetable oil, 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt, 2 tsp. mild curry powder (such as S&B), and 1 tsp. sugar in a medium bowl to combine. Add two ¾"-thick boneless rib-eye or New York strip steaks (about 1½ lb. total) and turn to coat. Let sit at room temperature 15 minutes.

Step 3

Heat a dry medium skillet, preferably cast iron, over medium-high until very hot. Cook steaks, turning every 2 minutes or so, until deeply browned and an instant-read thermometer inserted into thickest part registers 120°, 8–10 minutes for medium-rare. Transfer steaks to a wire rack set inside a rimmed baking sheet and let rest 10 minutes.

Step 4

Transfer steaks to a cutting board and slice against the grain. Line a platter with tender lettuce leaves; arrange steak on top. Spoon dressing generously over; top with cilantro and/or mint leaves. Serve with remaining dressing alongside.Do ahead: Steak can be marinated 1 day ahead. Cover and chill. Let sit at room temperature 15 minutes before cooking.