Preheat the oven to 350°F (175°C) and grease and flour a bundt pan.

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

Beat in the eggs one at a time, followed by the vanilla extract.

In another bowl, combine the flour, baking powder, baking soda, and salt.

Gradually add the dry mixture to the butter mixture, alternating with the sour cream. Mix until just combined.

Prepare the butter pecan filling by mixing the chopped pecans, melted butter, and brown sugar in a separate bowl.

Pour half of the cake batter into the prepared bundt pan, layer with the pecan filling, and then pour the remaining batter on top.

Bake for 60-70 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes before inverting onto a wire rack to cool completely.