Begin by preheating your oven to 350°F (175°C). Prepare a 9×5 inch loaf pan by generously buttering and flouring it to prevent sticking.

In a medium-sized bowl, whisk together the all-purpose flour, salt, and baking powder, ensuring they are well combined. Set this mixture aside.

Using a stand mixer with the whisk attachment, cream the butter on medium speed until it becomes smooth and creamy. Gradually add the sugar, beating until the mixture is light and fluffy. Pause to scrape down the sides of the bowl to ensure even mixing, then continue to beat for a few more seconds.

Incorporate the eggs one at a time, mixing well after each addition. It's important to scrape down the bowl periodically to ensure the mixture is well-blended and smooth.

Add the sour cream and vanilla extract to the mixture, beating until they are fully integrated. Again, make sure to scrape down the sides of the bowl to maintain a uniform mixture.

Gradually add the flour mixture to the wet ingredients, mixing on low speed until just combined. Use a spatula to scrape down the bowl and ensure there are no pockets of flour or butter remaining.

Pour the batter into the prepared loaf pan, spreading it evenly with a spatula. Smooth the top to create an even surface. Bake in the preheated oven for approximately 40 minutes, or until the center is set and a skewer inserted into the middle comes out clean.

Once baked, let the cake cool in the pan for about 10 minutes. Then, carefully transfer it to a cooling rack to cool completely before serving.