Preheat the oven to a temperature of 350º F. Subsequently, prepare a square baking dish by lightly greasing it either with butter or a non-stick agent.

In a medium-sized mixing bowl, combine 1 3/4 cups of flour with the baking powder and kosher salt. Stir until well-integrated.

In a separate, larger bowl, combine the room temperature butter, granulated sugar, and lemon zest. Utilizing an electric mixer, blend the components until the mixture is light in color and exhibits a fluffy texture. This process should take approximately 3-5 minutes.

Introduce the egg and vanilla extract into the large bowl and continue the mixing process until all ingredients are well-incorporated.

Gradually introduce the cultured buttermilk and previously prepared flour mixture into the large bowl. It's essential to alternate between these two components, ensuring that they blend seamlessly.

In a distinct bowl, coat the blueberries with the remaining 1/4 cup of flour. This procedure aids in preventing the berries from settling at the base of the bake. Once coated, incorporate the blueberries into the primary batter mixture.

Transfer the batter to the pre-greased baking dish. As a final touch, sprinkle the reserved granulated sugar uniformly over the surface of the batter.

Position the baking dish in the preheated oven and allow to bake for a duration of approximately 40 minutes. To confirm its readiness, insert a toothpick into the center of the bake—if it emerges clean, the bake is complete.

Once removed from the oven, it is imperative to allow the dish to cool prior to serving. The result should be a sophisticated and delightful Buttermilk Blueberry Breakfast Bake, ready for consumption.