In a small nonmetal bowl micro-cook butter or margarine, uncovered, on 100% power for 20 to 30 seconds or till melted. Stir in the beaten egg, corn syrup, sugar, and flour. Micro-cook, uncovered, on 50% power for 3 to 3 1/2 minutes or till slightly
thickened, stirring every 30 seconds. Stir in vanilla. Turn into pecan pie pastry. Arrange pecan halves atop pie. Micro-cook, uncovered, on 30% power for 1 1/2 to 2 minutes or just till set, rotating the dish a quarter-turn every minute. Cool before serving.