Prep. Preheat the oven to 350°F and grease a Bundt pan with nonstick baking spray.
Make the Bundt cake batter. Whisk together the lemon cake mix, lemon pudding mix, buttermilk, vegetable oil, eggs, milk, and lemon zest until smooth. Don’t over-mix.
Add the blueberries. In a medium mixing bowl, toss the blueberries together with the flour and then gently fold in the blueberries into the batter. Do not over-mix.
Bake. Pour the batter into the prepared Bundt pan and bake for 1 hour or until a toothpick inserted into the center comes out clean.
Cool. Allow the cake to cool in the pan for 15 minutes, then transfer it to a wire rack to cool completely.
Blueberry Glaze
Simmer. In a saucepan, combine the blueberries, powdered sugar, vanilla, and lemon juice. Cook over medium heat, stirring occasionally, until the blueberries break down and the mixture thickens. Remove from the heat.
Strain. Strain the blueberry mixture through a fine mesh sieve.
Make it creamy. Whisk the milk into the glaze.
Glaze the cake. Once the cake has cooled, drizzle the blueberry glaze over the top.