Sift 31/4 cups flour, baking soda and salt onto a sheet of waxed paper; set aside.
In a large bowl, with an electric mixer set at medium speed, beat softened butter with sugar and zest until the mixture is light and fluffy, about 2 minutes.
Add eggs, one at a time, beating until smooth and thick, about 3 minutes.
Add lemon juice and sour cream; mix well.
Mix in sifted dry ingredients and buttermilk until batter is well blended.
Toss the blueberries with the remaining 1/4 cup of cake flour. Gently fold them into the batter with a wooden spoon.
Pour batter into a lightly buttered and floured 10” bundt pan. Gently tap the bottom of the pan on the counter top a few times – this will help “settle” the batter into the pan.
Bake at 350 degrees for 50 to 60 minutes, until a toothpick inserted into the center of the cake comes out clean.
Set the pan on a wire rack for 10 minutes. Then very gently tap the bottom of the pan on the counter, ever so lightly, to help release the cake from the sides of the pan. Hold the rack upside down over the top of the pan, then invert the whole thing so the cake can release onto the rack.
Place the rack on a piece of waxed paper. Begin spooning glaze over the warm cake, scraping up the drippings from the waxed paper and reapplying them. This is rather a tedious process, but it is worth it!! Keep scraping the glaze off of the paper and drizzling it over the warm cake. If you think it would be less messy if you waited until it cooled, you are right, BUT you'd forfeit wonderful“soaking in” of the glaze into the warm cake…don’t be tempted!
Once you have drizzled, scraped and reapplied as much glaze as possible, sprinkle the top of the cake with one or two tablespoons of powdered sugar that has been shaken from a fine sieve.
This cake freezes very well, if you have leftovers. I slice it into serving pieces and freeze them individually so we can pop a piece out of the freezer anytime we want some, without having to slice through a frozen chunk of cake.
For the glaze:
Use a microplane, or the smallest grate on your cheese grater, to zest the lemon. Melt the butter in a small bowl; stir in the lemon juice, zest and salt. Stir in the powdered sugar until a smooth glaze forms. Set aside until you are ready to glaze the warm cake.