1. **Preheat & Prep:** Preheat your oven to 375°F (190°C). Lightly butter a 9-inch springform pan (or round cake pan) and line the bottom with parchment paper. This ensures the cake releases perfectly.

2. **Whisk Wet Ingredients:** In a large mixing bowl, beat the eggs and sugar on high speed with an electric hand mixer for about 5 minutes, until the mixture is thick, pale, and doubled in volume. Add the sour cream, oil, vanilla, and salt. Whisk on low speed just until combined.

3. **Add Dry Ingredients:** In a separate small bowl, whisk together the flour and baking powder. Add this to the wet ingredients in two batches, mixing on low speed (or folding by hand) until just incorporated. Do not overmix! Stir in the lemon zest and ½ tablespoon lemon juice.

4. **Prep Berries:** In a medium bowl, toss the rinsed (and well-drained) blueberries with the cornstarch and 1 teaspoon of lemon juice. Stir until the berries are coated and no dry white powder remains. This prevents them from sinking to the bottom of the cake.

5. **Assemble:** Pour about half of the batter into the prepared pan and spread it evenly. Top with half of the blueberries. Spread the remaining batter over the top, then scatter the remaining blueberries over the surface, pressing them slightly into the batter.

6. **Bake:** Bake for 45–55 minutes, or until a toothpick inserted into the center comes out clean. If the top starts browning too quickly after 30 minutes, loosely tent the pan with aluminum foil.

7. **Cool & Glaze:** Let the cake cool in the pan for 15–20 minutes, then remove the ring and transfer to a wire rack to cool completely. Whisk the powdered sugar and lemon juice together to make a smooth glaze. Drizzle generously over the cooled cake before serving.