Creating this Lemon Blueberry Sheet Cake is easy and straightforward if you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch sheet pan or line it with parchment paper.
2. Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
3. Cream the Butter and Sugar: In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy.
4. Add Eggs: Incorporate the eggs one at a time, mixing well after each addition.
5. Combine Wet Ingredients: Stir in the buttermilk, lemon zest, lemon juice, and vanilla extract until fully combined.
6. Combine Dry and Wet Mixes: Gradually add the dry mixture to the wet ingredients. Mix until just combined; do not overmix.
7. Fold in Blueberries: Gently fold in the blueberries, ensuring they are evenly distributed in the batter.
8. Pour into the Pan: Pour the batter into the prepared sheet pan, spreading it evenly.
9. Bake: Place the pan in the preheated oven and bake for 30-35 minutes. A toothpick inserted in the center should come out clean.
10. Cool: Once baked, remove the pan from the oven and let the cake cool in the pan for about 20-30 minutes, then transfer it to a wire rack to cool completely.

For the Lemon Glaze (optional)

11. Prepare the Glaze: In a small bowl, mix the powdered sugar, lemon juice, and zest until smooth. Adjust the consistency with more sugar or juice as necessary.
12. Glaze the Cake: Drizzle the lemon glaze over the cooled cake, allowing it to set before slicing.