Preheat oven to 350º. Generously butter and flour a 12-cup capacity Bundt cake pan, tap out excess flour. Set aside.
Sift flour, baking soda and salt onto a large sheet of wax paper, set aside. In large bowl of stand mixer, beat butter, sugar and lemon zest until light and fluffy. Add eggs one at a time, mixing after each, and lemon extract. Beat 3 minutes until mixture is thick and smooth.
Add the sifted ingredients alternately with the buttermilk, mixing well to combine. Add in this order, mixing after each addition: dry, wet, dry, wet, dry.
Toss blueberries with flour to coat. Use wooden spoon to stir into batter gently and evenly. Spoon batter into prepared pan and bang on counter a few times to settle batter. Smooth top with spatula. Bake for 55 to 60 minutes until toothpick inserted comes out clean.
Make glaze while cake bakes. Put sugar and lemon zest in food processor and pulse several times to combine well. With machine running, add lemon juice and melted butter through tube, blend well until smooth. Keep room temp until ready to use.
Let cake cool on rack for 10 minutes, gently invert cake onto rack. Place rack on a cookie sheet and brush lemon glaze all over warm cake, reapplying glaze as it drips onto cookie sheet. Let cake cool completely before serving.