Prep: Preheat the oven to 350°F. Line a 9x5 inch loaf pan with baking parchment.
Cream ingredients: Add butter and sugar to a large mixing bowl (OR the bowl of your stand mixer fitted with the paddle attachment). Mix until creamy and well combined. Add the eggs, lemon zest and lemon extract and continue creaming until light and fluffy.
Finish batter: In a separate bowl, combine flour, baking powder and salt. Mix buttermilk and lemon juice in a measuring jug. Add 1/2 of the flour mix to the bowl with the creamed ingredients and mix on the lowest setting until well combined. Add 1/2 of the buttermilk and lemon juice mix and continue mixing on low until smooth. Repeat with the remaining flour and buttermilk until you have a creamy batter.
Fold in blueberries: Add the floured blueberries to the batter and carefully fold in using a rubber spatula.
Bake: Pour the finished batter into the prepared loaf pan. Bake for 50-60 minutes, or until a toothpick inserted comes out clean. Cool in the pan for 5 minutes, then remove to a cooling rack to cool completely before slicing.
To make a lemon glaze, combine 1/2 cup powdered sugar with 1 tablespoon lemon juice and mix well. Drizzle over the cooled loaf.