Place apricots in small saucepan. Add just enough water to cover; bring to boil. Reduce heat and simmer, covered, 15 minutes. Drain apricots, reserving 3 tbs cooking liquid. Chop apricots fine. Combine in small sauce pan with reserved liquid, lemon peel, sugar, and cornstarch. Brink to boiling, stirring: boil 1 minute. Let filling cool 10 minutes. Spread evenly over shortbread crust. Sprinkls with walnuts. Bake 20 minutes. Let cool completely in pan on wire rack. Cut into bars.