Marinate turkey cutlets in 2 cups Catalina dressing, in a covered pan, the refrigerator for at least 4 hours.
Remove turkey from dressing and discard marinade. Grill turkey over medium flame about 8 minutes per side or until turkey is cooked throughout to an internal temperature of 165 degrees F and is no longer pink in the center.
Meanwhile, in hot butter, sauté red onion and peppers until vegetables are al dente. Remove from heat and stir in mango slices, toss lightly.
Place approximately 1 cup of shredded lettuce on each plate, top with grilled turkey cutlet and onion/mango sauté mixture.
Garnish with several cucumber slices and drizzle with 2 cups additional Catalina dressing. Dust with black pepper.