Grease and line a 20cm (9 inch) spring form cake tin.
Mix the flour, baking powder and bicarbonate of soda in a mixing bowl.
In a separate bowl, beat the butter, sugar and eggs for 2-3 minutes with an electric hand whisk until light and fluffy. Add the vanilla and Kvarg and continue beating for 1 more minute.
On a low speed add the flour mixture until combined, do not overmix.
Transfer the cake batter to the tin, top with the peach slices and scatter with the blueberries. Sprinkle the cake with a little granulated sugar (if using).
Bake for 45minutes to 1 hour, or until the cake is golden and a skewer inserted into the middle of the cake comes out clean.
Cool the cake in the tin for 10-15 minutes before carefully transferring to a cooling rack to cool completely.
Serve warm or cold with an extra serving of your favourite pot of Lindahls Kvarg.