1/2EaLemon JuiceNote: you should also add the juice of the 1/2 lemon
Preheat the oven to 350 degrees. Prepare a pan with either a silicon sheet or parchment paper. I have not been happy with how they brown using a cooking sheet, as they tend to stick a little.
In a medium-sized bowl, combine the flour, baking powder, sugar, salt, and lemon zest. Set aside.
In a large bowl, cream together the butter and sugar until smooth. Beat the 2 eggs in a small bowl, then mix in. Incorporate the sour cream.
Slowly add the flour mixture, blending well.
Carefully blend in the blueberries. Note: you may want to add a teaspoon of cornstarch to the blueberries beforehand, if they are thawed and giving off a lot of liquid.
Bake for 15 minutes, or until slightly brown around the edges. Let cool on baking sheet for another 10 minutes before moving to cooling rack.
To be honest, I really find it best to eyeball this. Basically you’re going to combine the powdered sugar, lemon zest, and just enough lemon juice to get a consistency you feel will spread well. I use a pastry brush.