Preheat your oven to 350°F (175°C). Generously grease and flour a 10-12 cup bundt pan, ensuring every crevice is coated.
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
In a large bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 2-3 minutes.
Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract, lemon zest, lemon juice, and sour cream until just combined.
Gradually add the dry ingredient mixture to the wet ingredients, alternating with the vegetable oil, beginning and ending with the dry ingredients. Mix on low speed until just combined. Be careful not to overmix.
Gently fold in the blueberries. If using frozen, toss them with a tablespoon of flour first to prevent sinking. Pour the batter evenly into your prepared bundt pan.
Bake for 50-60 minutes, or until a wooden skewer inserted into the center comes out clean. Let the cake cool in the pan on a wire rack for 10-15 minutes before inverting it onto the rack to cool completely.
While the cake cools, whisk together the powdered sugar and fresh lemon juice in a small bowl until smooth. Once the cake is completely cool, drizzle the glaze over the top.