Preheat the oven to 350 degrees.
Spray a large bundt pan with baking spray.
In a stand mixer fitted with the paddle attachment, cream the butter and sugar until smooth.
Add the lemon zest, vanilla extract, lemon oil, and eggs one at a time to the creamed butter and sugar mixture. Mix until just incorporated.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a small bowl, mix the fresh lemon juice and the buttermilk.
Starting and ending with the flour mixture, add the flour mixture alternatively with the buttermilk mixture and blend after each addition. Do NOT over mix.
Stir in the blueberries and pour the batter into the prepared bundt pan and spread until smooth.
Bake for 60 minutes. Sides should be golden brown and a wooden skewer inserted in the middle should come out clean. Do NOT over bake!
Allow to cool for 15 minutes before you invert the cake over a serving plate.
If desired, dust the top of the cake with powdered sugar.