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.