This is my coffee cake recipe for leisurely weekend baking. There are three kinds of flour in this batter, each one playing a different role. The graham flour adds flavor and a fine sandiness, while the all-purpose flour lightens the graham flour. The whole-grain pastry flour gives the cake its tender crumb. Caramelizing the apples concentrates the flavor of the fruit. You can use any apples you have on hand, but tart cooking apples like Granny Smiths work best, as their acidity offs