Makes 12 mini cakes
Preheat the oven to 350° F. Grease a 12 cup muffin tin with butter. Lightly flour and set aside.
With an electric mixer, beat the butter, sugar and zest on medium high until light and fluffy. Should take about 2 to 3 minutes.
Alternately, in 3 or 4 increments, add in the eggs and almond flour. Mix until well blended.
In a separate bowl, sift together the flour, baking powder and salt. With the mixer on low, blend the dry ingredients into the batter just until incorporated.
Add in the lemon juice and mix in until the batter comes back together. The batter will be very light and look slightly fluffy.
Spoon the batter evenly into the 12 muffin cups. Then press a few (about 3) blueberries into each and bake for 30 to 35 minutes. The edges will brown and a cake tester should come up clean. See photos.
Cool for 10 minutes then carefully tap out the cakes on to a cooling rack so they are upside down. Gently use a butter knife to coax them out, if they stick a little. Cool completely before icing. Decorate with a few fresh blueberries on the top.
Blend together the confectioner's sugar and the lemon juice, until you have a smooth but thick icing. Using a small spoon, drizzle the icing on top of each cake, letting it slowly drip down the sides.