Add boiling water to gelatin; stir until dissolved, about 2 minutes. Stir in cranberry sauce. Add pineapple, orange juice and lemon juice. Refrigerate until thickened, about 30 minutes. Stir in nuts. Pour into an 11x7-in. dish. Refrigerate until set. Cut into 12 squares; if desired, serve each with a lettuce leaf and a dollop of Miracle Whip.