Place liqueur in small bowl. In 1-quart saucepan, melt jam and butter over medium heat. Remove pan from heat; carefully add liqueur. Return to heat; cook 30 to 90 seconds, stirring constantly, until thickened. Pour over cake; let stand 5 minutes. Transfer cinnamon roll icing to 1-quart resealable food-storage plastic bag; cut off tiny piece of one corner, and pipe icing decoratively on top of cake.