Duck Breast with Arugula

Rinse the arugula and spin dry. Peel the onion and cut into strips. Whisk the oil, vinegar, pepper, and salt to make a vinaigrette. Rinse the duck breast, pat dry, and season with salt and pepper. Cut the skin gently, but do not mark the flesh. Fry until golden brown with the duck breasts, skin-side down for 5-7 minutes. Fry until the pores are closed.  Remove, cut in half and place on a parchment-lined baking tray for 5-10 minutes. Mix the arugula with the onion rings on a plate. Drizzle with the vinaigrette and place each half of the duck breast on the salad. Serve immediately.