Preheat your oven to 350°F (175°C). Grease a loaf pan generously with butter, then lightly dust it with flour. For easier removal, line the long sides with parchment paper.

In a medium bowl, whisk together the flour, salt, and baking powder until evenly combined. Set the mixture aside.

Place the softened butter into a large mixing bowl. Beat briefly until smooth, then gradually add the sugar. Continue mixing on medium speed until the mixture becomes pale, fluffy, and airy.

Crack the eggs into a separate bowl first. Add them to the butter mixture one at a time, mixing thoroughly after each addition to maintain a smooth batter.

Mix in the sour cream and vanilla extract until fully combined. The batter may appear slightly curdled, which is completely normal during this stage.

Gradually add the dry mixture to the wet ingredients. Mix on low speed just until combined, then gently fold the batter with a spatula to avoid overmixing.

Pour the batter into the prepared loaf pan and smooth the surface evenly. Tap the pan lightly on the counter to remove air bubbles.

Bake for about 40 minutes, or until a toothpick inserted into the center comes out clean. Smaller or deeper loaf pans may require additional baking time.

Allow the cake to cool in the pan for several minutes before transferring it to a cooling rack. Slice and serve warm or at room temperature with your favorite toppings.