I make this a lot...it's fast and it's so good....
5 oz arugula
1/3 cup extra-virgin olive oil
2 large garlic cloves, smashed
1 large sprig fresh rosemary
1 lb boneless sirloin (1 inch thick)
1 teaspoon salt
1 teaspoon black pepper
1 large shallot, thinly sliced crosswise
6 tablespoons balsamic vinegar
6 tablespoons red-wine vinegar
Put arugula on a serving platter
Heat oil with garlic and rosemary in a large skillet over high heat, turning garlic once or twice, until garlic is golden, about 4 minutes. Remove garlic and rosemary.
Meanwhile, cut steak crosswise into 1/8-inch-thick slices and toss with a little salt and pepper. Add meat to skillet all at once and sauté over high heat, tossing with a fork to color evenly, cook to desired doneness.
Pleace steak over arugula on plate, then add shallot to oil in skillet along with vinegars and remaining salt and pepper and boil 2 minutes. Pour dressing over steak and serve immediately