1. Beat butter or margarine until soft in medium-size bowl with electric mixer at high speed. Beat in 10X sugar, alternately with mixture of orange juice, corn syrup, lemon extract and salt, until thick and creamy.
2. Measure 1/2 cup of mixture into small bowl. Set remaining aside for frosting cake. Stir cottage cheese, walnuts and orange rind into the 1/2 cup until well blended. Use for filling.