Preheat oven to 180°C/160°C fan/gas 4. Grease and line a 20cm ring shaped cake tin with baking parchment.
Cream together the softened butter and sugar, until pale and fluffy. Add the lemon zest.
Sift the flour and bicarbonate of soda into the bowl, and add the ground almonds and eggs. Beat until just combined. Stir in the blueberries, reserving a few for decoration.
Fill the cake tin and bake for around 40 minutes, or until the cake begins to shrink away from the sides of the tin. Leave to cool for 5-10 minutes before turning out on to a wire rack, to cool completely.
Sift the icing sugar into a bowl and gradually add the lemon juice, until the glaze is just runny enough to fall from the spoon (probably about 3 tsp of juice). Decorate with the toasted almonds and remaining blueberries.