Grease the bottom and the sides of a 9-inch springform pan. Line the bottom of it with parchment paper and grease it too so that the cake can be removed very easily. Put it aside and preheat the oven to 350F.

In a medium bowl, whisk together the whole wheat flour, all purpose flour, salt, baking powder, cinnamon, nutmeg and cardamom.

In a large bowl, cream the butter and sugar using an electric mixer until pale and fluffy. Add the eggs one at a time. Then pour kefir and mix to combine.

Gradually add in the flour mixture and mix just until everything is combined. Don’t overmix.

Spread the batter in the prepared pan and place the apple slices and plum slices. Sprinkle brown sugar and cinnamon over them.

Bake for 40-45 minutes or until a toothpick inserted into the center comes out clean.

Run a knife around the edges of the pan when the cake is removed from the oven. Remove the springform edge and let the cake cool completely before slicing and serving.