Preheat oven to 325°F (165°C) and grease and flour a bundt or loaf pan
Beat butter and sugar until light and fluffy
Add eggs one at a time, mixing well after each
Mix in lemon zest, lemon juice, and vanilla
Gradually add flour and salt, alternating with sour cream
Mix just until smooth
Toss blueberries with flour and gently fold into batter
Pour batter into prepared pan and smooth the top
Bake for 70–80 minutes, tenting loosely with foil if browning too quickly
Cool in pan for 20 minutes, then turn out and cool completely
Drizzle with lemon glaze if using