Black Pepper Beef

Name: Black Pepper Beef
Ingredients: 12 ounces beef tenderloin, trimmed and cut into 1/2-inch-thick x 1-inch-wide x 2 1/2- to 3-inch-long strips; 1 1/2 teaspoons black pepper; 1 1/2 teaspoons kosher salt; 2 (2-ounce) lemongrass stalks , trimmed and cut into 4-inch pieces; 1 tablespoon canola oil; 10 fresh curry leaves; 1 small red onion , thinly sliced (about 1 3/4 cups); 1 (3/4-inch) piece fresh ginger, peeled and crushed; 2 small fresh green Thai chiles , thinly sliced (about 1 1/2 teaspoons); 2 tablespoons apple cider vinegar