1. Preheat oven to 325°F. Coat a 10-cup Bundt pan very thoroughly with flour-based baking spray — cover every ridge, curve, and the center tube. Set the prepared pan aside.

2. Whisk the flour, baking powder, baking soda, and salt together in a large bowl. Set aside.

3. Beat butter and sugar together on medium-high speed for 4–5 minutes until very pale, light, and fluffy. Add the lemon zest and beat for 1 more minute. Do not rush this step — the extended creaming creates the lift and texture in the finished cake.

4. Add the eggs one at a time, beating 30 seconds after each one. Scrape down the sides and bottom of the bowl with a spatula after every two eggs.

5. Add the sour cream, lemon juice, and vanilla extract. Mix on low until just combined. The batter may look slightly curdled at this stage — that is normal and corrects itself when the flour goes in.

6. Add the flour mixture in three additions, mixing on low between each one until just combined. Toss blueberries with 1 tablespoon of flour until coated, then fold in gently with a rubber spatula using only 6–8 folds. Overmixing breaks the berries and turns the entire batter purple.

7. Spoon the batter into the prepared Bundt pan and smooth the top. Bake at 325°F for 60–70 minutes. At the 40-minute mark, loosely tent with foil if the top is browning too fast. The cake finishes when a wooden skewer inserted in the thickest part comes out completely clean.

8. Cool in the pan for exactly 15 minutes. Invert onto a wire rack and cool completely before glazing — at least 1 hour.

9. For the glaze: Whisk powdered sugar, lemon juice, and lemon zest together until smooth. Start with 3 tablespoons of lemon juice; add more a teaspoon at a time until the glaze drips slowly from a spoon. Drizzle over the completely cooled cake. Let set for 20 minutes before slicing.