Pat the steaks dry with paper towels. Season with 2 teaspoons of the salt and 3 teaspoons of the pepper.
Heat 1 tablespoon of the olive oil in a cast-iron skillet over medium-high heat.
Add the steaks and cook to desired doneness, 5 to 6 minutes per side for medium-rare. Let rest for 10 minutes.
In a small bowl, whisk together the vinegar and the remaining olive oil, salt, and pepper.
In a large bowl, combine the radishes, cucumber, and lettuce with the vinaigrette. Slice the steak and serve with the salad.