Preheat the oven to 350°F (175°C). Grease and flour a 9 x 13-inch baking pan and set aside.
In a medium bowl, whisk together 2 1/2 cups flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, using an electric mixer, beat the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, beating well after each addition. Mix in the lemon zest, lemon juice, and vanilla extract until combined.
Add the dry ingredients to the wet ingredients in three additions, alternating with the sour cream, beginning and ending with the dry ingredients. Mix each addition just until combined; do not overmix.
Place the 2 cups of blueberries in a small bowl and toss with 1 tablespoon of flour to coat. Gently fold the coated blueberries into the batter.
Pour the batter into the prepared 9 x 13-inch pan and spread evenly.
Bake for 38-42 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and allow it to cool completely in the pan on a wire rack.
In a small bowl, whisk together the powdered sugar, 2 tablespoons lemon juice, and 1 teaspoon lemon zest until smooth to make the glaze.
Once the cake is completely cool, drizzle the lemon glaze evenly over the top.
Allow the glaze to set for about 15 minutes before slicing and serving.