Preheat oven to 350°F (175°C).

Grease a 9x5 inch loaf pan with butter or non-stick spray.

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt.

Gradually add the dry mixture to the creamed butter and sugar, alternating with buttermilk, beginning and ending with the dry ingredients. Mix just until combined.

Stir in the vanilla extract until just incorporated.

Pour the batter into the prepared loaf pan and smooth the top.

Bake for about 60 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer to a cooling rack to cool completely.