Preheat the oven to 350º F/ 180º C. Line two 7 inch/ 18 cm baking tins with circles of parchment paper.

In a bowl combine the flour, baking powder, baking soda and salt. Mix well to combine.

Place the butter and sugar in a large mixing bowl. Beat them with the paddle attachment of a stand mixer or alternatively with a hand mixer for 2-3 minutes, until light and fluffy.

Add the lemon zest, vanilla and the eggs, one by one. Continue beating until all ingredients are well incorporated.

Add the yogurt and beat again for few seconds until combined.

Gradually add the dry ingredients. Fold them gently with a rubber spatula or with the paddle attachment of the stand mixer at a low speed.

At the end fold the blueberries into the batter, washed and dried in advance. Mix very carefully, to avoid breaking them.

Divide the batter between the two pans.

Bake for about 20 minutes or until a toothpick inserted in the centre comes out clean (if you see blueberry juice on the tester, test in a different place).

Let the layers cool completely before assembling the cake.

In a large mixing bowl beat the cream cheese and the sour cream with the icing sugar (if using) until fluffy.

Gradually add the white chocolate (make sure it is not very hot). Beat with the mixer until smooth and creamy.

Place one cake layer on a serving plate and cover with ⅓ of the frosting. Place the second layer on top.

Spread the remaining frosting all around the cake. Let the cake sit in the fridge about 4-6 hours before serving.

Decorate with blueberries and lemon zest.