Pre-heat the oven to 180 °C and grease and line the base of 20cm/8" square cake tin.
Place the butter and sugar in a large bowl and beat together until light and fluffy – either using a free-standing mixer or a hand whisk.
Next, add an egg and a couple of spoons of the four and mix. Repeat for the remaining 3 eggs. Adding a little flour helps prevent the mix from curdling.
Beat in the lemon rind and then gently fold in the remaining flour and the ground almonds. At this point you want to add enough lemon juice to create a dropping consistency. You want the mixture to be soft enough to fall—or “drop”—from a spoon after a gentle nudge, but not too runny. Therefore, add the lemon juice a tsp at a time.
Gently fold in three-quarters of the blackberries turning them gently into the batter so as not to crush them. Then pour into the prepared cake tin. Scatter over the remaining berries and lightly push them into the batter.
Bake in the pre-heated oven for 45 minutes until firm to the touch. You should be able to insert a wooden toothpick in the centre and it comes out clean (no uncooked batter attached).
Just before taking the cake out of the oven, you want to make the quick drizzle icing. Place the lemon juice and sugar in a bowl and mix together until the sugar is no longer grainy.
Remove the cake from the oven and place on a wire rack, still in its tin. Take a wooden toothpick and prick the cake all over. Spoon the lemon drizzle icing slowly over the cake – you want to try and get that lovely lemon flavour to soak through the holes in the sponge.
Leave in the tin until completely cold and then cut into 12 or 16 squares, depending on how generous you want your slices.
Notes
You could make this recipe with other fruit. Raspberries or blueberries work well.
This recipe could also be made into muffins, rather than a cake, by sharing the batter amongst a 12-hole muffin tin and drizzling over the icing in the same way. You would need to reduce the baking time to 30 minutes.