Preheat the oven to 180C fan / 200C / gas 6. Grease and line a 2lb loaf tin or use a silicon loaf.
Place the butter, sugar, lemon zest, 2 tablespoon sof lemon juice and vanilla in the bowl of a free-standing food mixer with the paddle attachment in place. Beat on a high speed for 3-4 minutes, until light, then lower the speed to medium.
Add the eggs, slowly, scraping down the sides of the bowl. The mix will probably split a little but it will come back together. Add the flour, a pinch of salt and the ground almonds in three goes and then gently fold in 150g of blueberries and pour into the prepared loaf tin.
Bake for 15 minutes in the preheated oven, then sprinkle the remaining 50g of blueberries over the top of the cake. Return to the oven for another 15 minutes, until the cake is golden-brown but still uncooked. Cover loosely with tinfoil and continue to bake for 25-30 minutes, until risen and cooked. Test by inserting a knife or skewer into the middle and it is ready if it comes out clean. Remove from the oven and set aside, in its tin, to cool for 10 minutes, then remove from the tin and place on a wire rack to cool completely.
Meanwhile, make the icing. Put the remaining tablespoon of lemon juice into a bowl with the icing sugar and whisk until smooth. Pour over the cake and gently spread out: the blueberries on the top of the cake will bleed into the icing but don't worry about this as it looks fine.
This is an easy, moist and zingy cake which keeps well, for 3 days, stored in an airtight container at room temperature. It won't last long. It also freezes well.
I haven't made it with raspberries yet but I think that it would work well with them.