Mix the eggs, then add baking powder and salt and mix. Add sugar gradually. Beat until thick and lemon colored. Add flour and vanilla. Pour into 10 x 15 inch greased pan and bake 13 minutes at 400 degrees. Invert cake on a cloth, sprinkled with confectioners sugar. Trim edge and roll (cloth and all); cool. Unroll and fill with jelly or pudding and roll up again without cloth.