Preheat the oven to 180˚C/ 160˚C fan/ 356˚F/ 320˚F convection.
Line a 20 cm / 8 inch round baking tin with baking paper.
In a stand mixer or with electric beaters, beat the butter, sugar and lemon zest together until light and fluffy.
In a separate bowl mix the almond meal with the baking powder.
Break the eggs into a small bowl then whisk together with a fork. Add the almond extract and whisk to combine.
Add the flour mixture to the sugar and butter and stir, then add the eggs and mix until well combined. The batter will seem very thick.
Gently stir in the blackberries – try not to stir too much or the colour can bleed into the cake.
Spoon the batter into the prepared tin and spread lightly with the back of the spoon to get an even top, then sprinkle over the almonds in an even layer.
Place into the oven and bake for 40 minutes, until a skewer inserted into the middle of the cake comes out clean.
If some batter sticks to it then place back into the oven for another 5-10 minutes.
Leave in the tin for 10 minutes before carefully removing it from the tin to a wire rack to cool completely.
To serve, dust with icing sugar, an optional step but does make the cake look pretty!
Notes
STORAGERoom temperature: store in an airtight container for up to 3 days at room temperature.Freezer: ideally freeze before dusting with icing sugar. Wrap the cake well and freeze for up to 2 months.