– 1 ½ pound beef tenderloin
– ½ cup stone ground dijon mustard
– 1/4 cup freshly ground coarse black pepper
– 2 tablespoons olive oil plus more for drizzling
– 2 tablespoons salted butter
– coarse sea salt to taste
– ¼ cup capers drained
– ½ cup baby arugula
– ½ lemon or to taste