Preheat your oven to 350°F. Grease a 9 x 5-inch loaf pan with nonstick spray and line with parchment paper.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside 1 tablespoon for coating the blueberries.

In a large mixer bowl, beat the butter and sugar on medium speed until light and fluffy, about 3 minutes. Beat in lemon zest and vanilla.

Reduce mixer speed to low and add eggs one at a time. Combine milk and sour cream in a small bowl, then add flour mixture in three parts, alternating with the milk mixture, beginning and ending with flour. Mix just until combined.

Toss the blueberries with the reserved flour, then fold them gently into the batter.

Pour the batter into the prepared pan and smooth the top. Bake for 56 to 62 minutes, until it springs back when touched and a toothpick comes out with crumbs.

While baking, make the lemon syrup by simmering lemon juice and sugar in a saucepan over medium heat until dissolved and slightly thickened.

Brush the hot loaf with syrup immediately after removing from the oven. Cool in the pan for 10 minutes, then remove and cool completely.

Whisk together glaze ingredients until smooth. Drizzle over the cooled loaf and let set before slicing.