Heat oven to 375 degrees Fahrenheit/200 degrees Celsius.
Grease a 9" loaf pan (21-centimeter) with butter, or line it with a parchment paper sling. Set the pan aside.
Place butter, sugar, lemon zest, and vanilla extract in the bowl of a stand mixer fitted with the paddle attachment.
Beat on high speed for 3 to 4 minutes, until light, then lower speed to medium.
Add egg yolks, scraping down the sides of the bowl a few times as necessary.
Add to a large bowl.
Wipe out the bowl of the stand mixer and add the egg whites, beat on high until slightly stiff peaks form 3-4 mins.
In a separate bowl, whisk together flour, baking powder, salt and almond flour.
Add that to the large bowl with the sugar/butter mixture, mix well until well incorporated.
Fold in about 3/4 of the blueberries by hand, then add the egg whites and fold into mixture, do not overmix.
Scoop batter into the prepared loaf pan.
Bake for 15 minutes, then sprinkle the remaining blueberries and almonds over the top of the cake.
Return to the oven for another 15 to 20 minutes, until cake is golden brown but still uncooked. Cover loosely with foil and continue to cook for another 25 to 30 minutes, or until risen and cooked, and a knife inserted into the middle of the cake comes out clean.
Remove from oven and set aside in its pan to cool for 10 minutes before removing cake from pan and placing on a wire rack to cool completely.
In the meantime, make the icing: Add lemon juice and sugar to a bowl and whisk together until smooth, adding a bit more juice if necessary, just until the icing moves when you tilt the bowl. Pour over the cake and gently spread out.
Once completely cooled slice and serve.
Find more of Pamela's gluten free recipes at PamelasGlutenFreeRecipes.com.