Preheat oven to 325°F (165°C). Grease and flour a 10-inch bundt pan or two 9×5-inch loaf pans.
In a medium bowl, sift together 2 cups flour, baking powder, and salt. Set aside.
Toss blueberries with the remaining tablespoon of flour in a separate bowl.
In a large bowl, cream butter and sugar with an electric mixer for 4-5 minutes until light and fluffy.
Add eggs one at a time, beating well after each addition. Scrape down the sides of the bowl as needed.
Mix in vanilla extract until fully incorporated.
Reduce mixer speed to low. Add the flour mixture in three parts, alternating with sour cream, beginning and ending with flour. Mix just until combined.
Gently fold in the flour-coated blueberries and lemon zest (if using) with a rubber spatula.
Transfer batter to prepared pan(s), smoothing the top.
Bake for 60-75 minutes for bundt pan, or 50-60 minutes for loaf pans, until a toothpick inserted in center comes out clean.
Cool in pan for 15 minutes, then invert onto a wire rack to cool completely.
