Mix together sugar, vanilla bean seeds, eggs, flour, baking powder and salt.
Slice Granny Smith apples ultra thin using a mandolin, saving the favorite slices for the top.
Let the apple slices stand for 15 minutes to release liquid and loosen the batter.
Use a slotted spoon to pile the apple slices into a prepared pan, leveling them out as you go.
Pour the remaining batter over the surface of the apples.
Bake the cake at 350 degrees for about 90 minutes.
Brush the cake with apple jelly for shine.
Serve the cooled cake with a dollop of cinnamon-spiked whipped cream.
