In a medium bowl, sift together the flour, baking powder, and salt. In a separate large bowl, whisk together the sour cream, sugar, eggs, lemon zest, oil, and vanilla paste.
Add the flour mixture to the egg mixture, stirring until combined. Fold in fresh blueberries very gently, then pour the cake batter into the prepared Bundt cake pan.
Once baked, remove from the oven and let the cake cool for about 5 minutes, then put a plate or serving dish on top of the Bundt cake pan and flip the cake onto the serving plate.