Preheat oven to 350°
In a large bowl, cream butter, sugar, and lemon zest together until light and fluffy, about 3 to 5 minutes.
Add eggs one at a time and beat on low an additional minute after each egg, adding vanilla with the last egg.
In a separate large bowl add dry ingredients and stir to combine.
Alternate adding 1/3 of the dry ingredients and the buttermilk at a time to the butter/sugar/lemon zest/egg mixture. Don't over mix, just combine the ingredients.
In small bowl, toss the blueberries with a tablespoon or two of flour to coat the blueberries (this helps keep them from sinking to the bottom when baking). Gently fold blueberries into batter.
Grease and flour 2 large loaf pans.
Divide batter between the pans and bake for about 50-55 min. Start checking for doneness after 45 minutes.
Let loaves cool about a half hour, remove from pans. Drizzle glaze over top of loaves.