Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking pan with butter or nonstick cooking spray. Line with parchment paper if desired for easier lifting and slicing.

In a medium bowl, whisk together 2½ cups flour, baking powder, and salt. Set aside.

In a large mixing bowl, beat the softened butter and granulated sugar for 2 to 3 minutes, until light and fluffy.

Add the eggs one at a time, beating well after each addition. Mix in the lemon zest, lemon juice, and vanilla extract.

Add the flour mixture in two additions, alternating with the sour cream. Mix on low speed just until combined. Do not overmix.

In a small bowl, toss the blueberries with 1 tablespoon flour. Fold the coated blueberries gently into the cake batter with a spatula.

Spread the batter evenly into the prepared pan. Bake for 35 to 42 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Let the cake cool in the pan for 15 minutes, then allow it to cool completely before glazing.

To make the glaze, whisk powdered sugar with 3 tablespoons lemon juice until smooth. Add more lemon juice, a few drops at a time, until the glaze reaches a thick but pourable consistency. Stir in optional lemon zest.

Drizzle the lemon glaze over the cooled cake. Let the glaze set for 10 to 15 minutes before slicing. Garnish with fresh blueberries or lemon zest if desired.