Preheat oven to 350 degrees Fahrenheit. Spray a 9 x 5 baking pan with nonstick cooking spray,
In the bowl of a stand mixer cream butter and sugar until light and fluffy about 4 minutes on medium speed. In a medium bowl combine the flour, baking powder, and kosher salt then whisk together. Set aside.
Add the eggs one at a time to the butter mixture beating until incorporated. Scrape the bowl with a spatula in between each one.
Add half of the flour mixture and beat until incorporated then repeat with the other half. Scrape the sides of the bowl with a spatula to make sure everything is mixed together.
Add the vanilla and sour cream then beat until incorporated. Scrape the batter into the greased baking dish and bake until golden brown and a toothpick comes out clean, about 65 to 75 minutes.