Preheat the oven to 350˚F. Line a 9x9 or 8x8 baking pan with parchment paper and set aside.
In a large bowl mix together butter, sugar, and brown sugar. Add in egg and vanilla and continue mixing until combined.
Add in flour and baking powder and mix to combine. Fold in butterscotch chips and chopped pecans until incorporated.
Place batter into prepared baking dish and bake for 33 minutes.
Allow butterscotch blondies to cool in pan for about 10 minutes, then remove by lifting up on parchment paper and allow to cool another 10 minutes. Drizzle the top with butterscotch topping and sea salt flakes. Cut into squares and serve.