In small bowl, combine flour, baking powder and salt; set aside. In large bowl, beat eggs and sugar with electric mixer on medium-high speed until thickened and pale yellow in color, about 5 minutes. Add lemon zest and juice. Using a spatula, fold flour mixture into egg mixture in three additions. Fold in cooled butter. Cover with plastic wrap and refrigerate at least 30 minutes and up to 1-1/2 hours.