Preheat your oven to 350°F (175°C) and line a cupcake pan with liners.
In a large bowl, combine flour, sugar, baking powder, and salt, whisking until well combined.
In another bowl, beat the butter until creamy. Gradually add sugar and mix until light and fluffy.
Beat in eggs one at a time, followed by vanilla extract, mixing until incorporated.
Gradually add the dry mixture to the wet mixture, alternating with buttermilk until fully combined.
Gently fold in the butterscotch sauce to the batter for that rich flavor.
Fill each cupcake liner about 2/3 full with batter.
Bake for 18-20 minutes or until a toothpick comes out clean. Allow cooling in the pan for 5 minutes before transferring to a wire rack.
While cooling, prepare your frosting using butter, powdered sugar, vanilla, and butterscotch sauce until creamy.
Once cooled, frost the cupcakes generously and drizzle with additional butterscotch sauce, if desired.