Begin by preheating your oven to 350°F (175°C). Prepare a 9×5-inch loaf pan by greasing it with butter or non-stick spray, ensuring an easy release after baking.

In a large mixing bowl, cream the softened unsalted butter and granulated sugar together using an electric mixer. Beat on medium speed until the mixture is light and fluffy, which should take about 3-5 minutes.

Add the eggs one at a time, mixing well after each addition. Then, stir in the pure vanilla extract and the scraped seeds from the vanilla bean. Mix until well combined.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to the butter and sugar mixture, mixing on low speed until just combined.

Add the sour cream, lemon zest, and fresh lemon juice to the batter. Pour in the whole milk while continuing to mix until the batter is smooth. Avoid overmixing to keep the cake tender.

Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Bake in the preheated oven for about 60-70 minutes, or until a toothpick inserted into the center comes out clean. If the top begins to brown too quickly, lightly cover it with aluminum foil.

Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes. Carefully transfer it to a cooling rack to cool completely.

While the cake cools, mix the powdered sugar, milk, and vanilla extract in a small bowl until smooth. Adjust the consistency with more milk or powdered sugar as needed.

Once the cake has cooled completely, drizzle the glaze over the top. Allow it to set for a few minutes before slicing. Serve with your favorite beverage and enjoy!