Heat oven to 350 degrees Fahrenheit/190 degrees Celsius (conventional oven). Grease a 9- or 8-inch/21-centimeter loaf pan with butter, line it with a parchment paper sling and butter the paper. Set the pan aside.

Place butter, sugar, lemon zest and both extracts 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 eggs in three additions, scraping down the sides of the bowl a few times as necessary. The mix may split a little but don’t worry: It’ll come back together once you add the dry ingredients.

In a bowl mix the dry ingredients. Toss the blueberries with a tablespoon of the dry ingredients so that they wouldn't sink, then fold them into the batter all at once.

Pour in prepared pan. Bake uncovered for an hour 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.

When cake is cool, make the icing: Add lemon juice and icing 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. Let icing set (about 30 minutes), slice and serve.