1 lb boneless top loin steak or sirloin (1 inch thick)
1 teaspoon salt
3/4 teaspoon black pepper
1 large shallot, thinly sliced crosswise
1 1/2 tablespoons balsamic vinegar
1 1/2 tablespoons red-wine vinegar
Garnish: freshly ground black pepper
Directions
Mound arugula on a large platter.
Heat oil with garlic and rosemary in a 12-inch heavy skillet over high heat, turning garlic once or twice, until garlic is golden, about 4 minutes. Discard garlic and rosemary.
Meanwhile, cut steak crosswise into 1/8-inch-thick slices and toss with 3/4 teaspoon salt and 1/2 teaspoon pepper. Add meat to skillet all at once and sauté over high heat, tossing with tongs to color evenly, about 1 minute for medium-rare. Arrange steak over arugula using tongs, then add shallot to oil in skillet along with vinegars and remaining 1/4 teaspoon each of salt and pepper and boil 2 minutes. Pour dressing over steak and serve immediately.
