Make turkey cutlets: Pat the turkey dry and spread the seasoned flour on a plate. In a small shallow bowl, beat eggs lightly, and season them with salt and pepper. In another small shallow bowl, stir together bread crumbs and Parmesan.
Dredge cutlets in flour, shaking off excess, and dip in egg, letting excess drip off. Coat cutlets with bread crumb mixture and put on a waxed-paper-lined tray. You can at this point chill cutlets for 15 minutes.
In a 12-inch non-stick skillet, heat oil over moderately high heat until hot but not smoking and saute cutlets 1 1/2 to 2 minutes on each side, or until golden and just cooked through. Remove skillet from heat.
Make the salad: In a bowl, combine watercress and onion and drizzle with oil, tossing to coat. Add lemon juice and salt and toss well.
Transfer cutlets with a slotted spatula to paper towels to drain briefly and arrange on plates. Top cutlets with salad and serve with lemon wedges.