Place egg whites in a small bowl; let stand at room temperature 30 minutes. Preheat oven to 350°. Drain apricots, reserving 3 tablespoons syrup (discard remaining syrup); set aside., Place butter in a 9-in. square baking dish. Place in oven 3-4 minutes or until butter is melted; swirl carefully to coat evenly. Sprinkle with brown sugar. Arrange apricot halves in a single layer over brown sugar, cut side up., In a small bowl, whisk flour, baking powder and salt. In a large bowl, beat egg yolks until slightly thickened. Gradually add sugar, beating on high speed until thick and lemon-colored. Beat in reserved apricot syrup. Fold in flour mixture., With clean beaters, beat egg whites on medium speed until stiff peaks form. Fold into batter. Spoon over apricots. Bake 35-40 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes before inverting onto a serving plate. Serve warm.