- 975 g (~9 – 10) small apples
- 2 1/2 cups (300 g) whole wheat pastry flour
- 1 tspn salt
- 1 tspn baking powder
- 1/4 tspn ground cinnamon
- 1 cup + 5 Tbspn (297 g) butter, softened
- 1 1/2 cups (300 g) light brown sugar, lightly packed
- 3 large eggs, at room temperature
- 1/2 cup buttermilk
- 90 g walnuts, coarsely chopped
- Preheat oven to 180 degrees C. Grease and flour the insides and bottom of a 9 x 3-inch round cake pan. Line the bottom with a parchment paper round. Wrap the outside of the pan with bake even strips (see note).
- Using a mandolin, very thinly slice two of the apples. Arrange the slices on the parchment paper at the bottom of the cake pan, starting from the inside and working outwards.
- Finely grate the remainder of the apples, resulting in about 600 g of grated apple. Set aside.
- In a bowl, whisk to combine the whole wheat pastry flour, salt, baking powder, and ground cinnamon. Set aside.
- In a separate bowl, combine the butter and brown sugar. Beat on medium until light and fluffy, about 2 to 3 minutes. Add in the eggs one at a time, beating well after each addition. Beat in the grated apple until combined. Add the flour mixture in two parts, alternating with the buttermilk. Beat briefly until combined, but do not overmix. Fold in the chopped walnuts.
- Carefully pour the batter into the prepared cake pan. Use the back of a spatula to gently press the batter into the apple slices on the bottom and to smooth out the top. Tap the bottom of the pan gently on a counter to release any air bubbles.
- Bake the cake for about 1 hour and 5 minutes to 1 hour and 15 minutes. The cake is done when the top is golden brown and just beginning to pull away from the edges, and when a toothpick inserted in the center of the cake comes out cleanly. Remove the cake from the oven and transfer to a wire rack. Let cool for 15 minutes, until the pan is cool enough to touch. Run a sharp, thin knife along the inside edge of the pan to loosen the cake. Invert the cake onto a plate, remove the pan and parchment round. Let cool completely.
Note regarding bake even strips: Normally, I’d say that bake even strips were optional, but because this cake will be flipped on its head, a flat top is preferable. If you don’t have bake-even strips, try using a 9 x 3-inch springform and trimming the top before flipping the cake over.
Note regarding peeling apples: For the sliced apples on top of the cake, I prefer to leave the skins on so that there are borders to the design on top of the cake. Just make sure to use a mandolin to make very thin slices so that the peels don’t get chewy. For the grated apples inside the cake, I left the peels on because the apples are finely grated and a teeny bit of peel doesn’t bother me much. If you’d like a smoother texture, you can peel these apples first before grating them.