Preheat the oven to 175°C (350°F).
Mix all-purpose flour, almond flour and baking powder in a bowl.
Whip the eggs and sugar in a stand mixer on high speed for about 1 minute, then add yogurt and mix until well incorporated.
Add oil and orange zest and continue mixing until the oil is well incorporated.
Set the mixer to medium speed and add the flour mixture one tablespoon at a time until you have a uniform smooth batter.
Line a 23cm (9 inch) cake tin with baking paper or alternatively brush the inside of the tin with softened butter.
Pour the batter in the tin and top with blackberries.
Bake in the preheated oven for 35-40 minutes or until the toothpick comes out clean.
Leave to cool in the tin before taking the cake out.