In a small bowl, sprinkle gelatin over cold water; let stand for 1 minute. Stir in boiling water until gelatin is completely dissolved. Stir in the orange juice, sugar, lemon juice, orange liqueur and orange zest until sugar is dissolved. Refrigerate until thickened, about 1 hour.
Fold in whipped cream and cake cubes. Transfer to a greased 11x7-in. dish. Cover and refrigerate for at least 2 hours before serving.