Add softened small cubes of butter to a mixing bowl & beat with an electric mixer till spreadable. Add in the Caster sugar & beat till paler in colour, spreadable & aerated. Add in the eggs, one at a time, mixing in-between each addition.
Sieve over the flour & baking powder & then add in the ground almonds. Mix briefly by hand, before adding in the boiled water. Beat the mixture together, only until combined & no dry patches remain at the bottom of the bowl. Then fold in the lemon zest.
Wash the fresh blueberries in warm water & then pat dry before tossing in a few tsp flour. **For frozen blueberries, no defrosting or washing required. Just remove from the freeze right before adding to the cake batter & toss in the flour. Fold the blueberries into the batter, in 3 increments, with a spatula. preheat your oven to: 180°c/160°c fan oven/350°f/Gas Mark 4
Add cupcake/muffin paper liners to a cupcake tray & divide the cake batter between them. Tap the tray on the counter/worktop and pop them in the centre of the oven to bake for about 20 minutes. Bake till risen, golden and a toothpick comes out clean of crumbs. Leave to cool while still in the cupcake tray.