In a 15-ounce custard cup micro-cook the butter or margarine, uncovered, on 100% power for 30 to 40 seconds or just till melted. Swirl the butter in the custard cup, coating sides and bottom. Pour the excess butter from the custard cup into the beaten egg. Stir in the dark corn syrup and vanilla. Stir together flour and baking powder. Stir flour mixture into egg mixture. Gently fold in chopped pecans. Pour the pecan mixture into the buttered 15-ounce custard cup. Micro-cook, uncovered, on 50% power for 3 to 4 minutes or till the pecan mixture is just set, rotating the custard cup a half-turn every minute. Sift a little powdered sugar atop. Serve warm with light cream, if desired.