Preheat your oven to 350°F (175°C).

In a 9-inch round cake pan, melt the butter over low heat.

Once melted, remove from heat and sprinkle the brown sugar evenly over the butter.

Arrange the chopped pecans on top of the brown sugar mixture.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

In a separate large bowl, beat the granulated sugar and eggs together until light and fluffy.

Stir in the vanilla extract.

Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk, starting and ending with the dry ingredients. Mix until just combined.

Pour the batter over the pecan mixture in the cake pan, spreading it evenly.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then carefully invert it onto a serving plate.

Let it cool completely before slicing.