Preheat the oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a large bowl, cream together the softened butter and brown sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with buttermilk.
Stir in the vanilla extract and butterscotch chips until evenly distributed.
Divide the batter between the prepared cake pans and smooth the tops.
Bake for 30-35 minutes or until a toothpick inserted comes out clean.
Allow the cakes to cool in the pans for 10 minutes before transferring to wire racks.
Once cooled, frost with your favorite butterscotch frosting.