Whisk dry ingredients. Preheat an oven to 350°F / 175°C. Spray a 10-cup bundt pan with nonstick spray. In a large mixing bowl, whisk together 2½ cups flour, ¾ tsp baking powder, ¼ tsp baking soda, and ½ tsp Kosher salt. Reserve 1 Tbsp of the flour mixture to toss with the blueberries.
Cream butter and sugar. In the bowl of a stand mixer fitted with the paddle attachment, beat 10 Tbsp room temperature butter, 1¼ cup sugar, and lemon zest on medium speed until light and pale. Reduce the speed to low, then add room temperature eggs one at a time.
Whisk remaining wet ingredients. In a 2 cup measuring cup, combine 1 cup buttermilk, 2 Tbsp lemon juice, and 1 tsp vanilla extract, then whisk.
Add flour to wet ingredients. Add ⅓ of the flour mixture to the creamed butter, beating well, then add ½ of the buttermilk mixture. Once incorporated, repeat once again, alternating between flour and buttermilk, ending with the final flour mixture. Toss blueberries with reserved 1 Tbsp flour, then gently fold into the batter.
Bake the bundt cake. Spoon the batter into prepared bundt pan, then smooth with an offset spatula. Tap the pan sharply on the counter 2-3x to reduce air bubbles. Bake for 50 minutes, until cake is golden, springs back to the touch, and a tester inserted in the center comes out clean.
Cool slightly, then invert. Allow cake to cool in the pan on a wire rack for 15 minutes, then carefully invert onto rack and cool completely.
Make the glaze. Whisk together 1 cup powdered sugar, 2 Tbsp lemon juice, lemon zest, 1 tsp milk, and a pinch of salt in a small bowl. Drizzle glaze over cooled cake, then let set before serving. Store leftovers in an airtight container at room temperature.