Preheat oven to 375 degrees.
Cover the bottom of a 12-by-16 inch jelly roll pan with parchment paper.
Grease and flour the bottom and sides of pan. In bowl of an electric mixer, beat sugar, egg yolks, and milk until light and creamy. Beat egg whites with cream of tartar until medium firm. Combine flour and baking powder.
Fold flour in egg yolk mix alternately with egg whites. Spread cake mix over the whole surface of pan.
Bake 12 minutes or until center of cake is set. Sprinkle a clean towel with confectioner's sugar.
Turn the cake over towel. Roll into a jelly roll. Cool. Unroll and fill with apricot jam.
Roll again and cool before serving.