Step 1: Preheat your oven to 325°F (160°C). Grease and flour a 10-12 cup Bundt pan or a 9x5 inch loaf pan. Set aside.
Step 2: In a small bowl, gently toss the blueberries with 1 tablespoon of the all-purpose flour. This helps prevent them from sinking.
Step 3: In a large mixing bowl, using an electric mixer, cream together the softened butter and granulated sugar until light and fluffy, about 3-5 minutes.
Step 4: Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
Step 5: In a separate medium bowl, whisk together the remaining 2 cups + 2 tablespoons all-purpose flour, baking powder, and salt.
Step 6: Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Begin and end with the dry ingredients. Mix until just combined, being careful not to overmix.
Step 7: Gently fold in the lemon zest and the floured blueberries until evenly distributed.
Step 8: Pour the batter evenly into your prepared pan. Bake for 60-75 minutes for a Bundt pan or 70-85 minutes for a loaf pan, or until a wooden skewer inserted into the center comes out clean.
Step 9: Let the cake cool in the pan for 10-15 minutes before inverting it onto a wire rack to cool completely.
Step 10: While the cake cools, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar and fresh lemon juice until smooth and pourable. Add more juice for a thinner glaze or more sugar for a thicker one.
Step 11: Once the cake is completely cool, drizzle the lemon glaze generously over the top. Allow the glaze to set before slicing and serving.