Preheat oven to 350°F**. Grease a Bundt cake pan with cooking spray or neutral oil. Then, whisk together the flour, Kosher salt, and baking soda in a small bowl. Set aside.

In a medium mixing bowl, cream the butter and sugar until incorporated, about 4 minutes. (The mixture may be a little sandy). Add the lemon zest and vanilla. Then, mix in the eggs one at a time until incorporated.

Add half of the flour mixture, followed by half of the sour cream. Repeat with the remaining flour mixture and sour cream, just until mixed. A few lumps are ok! Pour the batter into the Bundt cake pan until smooth.

Bake for 60-75 minutes*** until an inserted toothpick comes out with just a few moist crumbs. Let cool in the pan for about 15 minutes, and then let cool completely on a cooling rack.

Place a fine-mesh sieve over a small bowl and set aside. If you are using frozen blackberries, let them thaw completely on the counter or heat them in a saucepan over medium heat, stirring constantly, until completely thawed.

Pour the blackberries in a food processor (or blender) and puree the berries until they are completely smooth. Strain the blackberry puree through the fine-mesh sieve, pressing with a wooden spoon to get out as much juice as possible. Discard the leftover seeds and pulp.

In a medium bowl, whisk together the powdered sugar and 1/4 cup of blackberry juice until a thick glaze forms. Thin the glaze with milk (or blackberry juice) 1 Tablespoon at a time until your glaze is thick but pourable. It should be the consistency of honey.

Pour the blackberry glaze over the cooled sour cream lemon pound cake. Decorate as desired. Let the glaze set at room temperature for at least 20 minutes before serving.