Creating a delicious Lemon Blueberry Sheet Cake can be straightforward if you follow these steps carefully:

1. Preheat the Oven: Set your oven to 350°F (175°C). Prepare a 9×13-inch baking pan by greasing it lightly.
2. Mix Dry Ingredients: In a bowl, whisk together the flour, baking powder, baking soda, and salt. Set this mixture aside.
3. Cream Butter and Sugar: In a large bowl, using an electric mixer, cream the softened butter and granulated sugar until light and fluffy.
4. Add Eggs: Beat in the eggs, one at a time, ensuring each is fully mixed before adding the next.
5. Incorporate Wet Ingredients: Add the buttermilk, lemon zest, lemon juice, and vanilla extract to the mixture. Mix until combined.
6. Combine Dry Ingredients: Gradually add the dry flour mixture to the wet ingredients, mixing until just combined. Be careful not to over-mix.
7. Fold in Blueberries: Gently fold the fresh blueberries into the batter, ensuring they are evenly distributed without mashing them.
8. Pour Batter: Pour the batter into the prepared baking pan, spreading it evenly.
9. Bake: Place the cake in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
10. Cool the Cake: Once baked, remove the pan from the oven and let the cake cool for about 15-20 minutes in the pan. Then, transfer to a wire rack to cool completely.
11. Dust with Powdered Sugar: If desired, dust the top with powdered sugar just before serving for an elegant touch.

These step-by-step instructions will guide you through the process of creating your very own Lemon Blueberry Sheet Cake!