Preheat oven to 325 degrees F. Spray a 9x13-inch baking pan with nonstick cooking spray and set aside.
In a medium bowl, whisk together flour, baking soda, and sea salt. Set aside.
In the bowl of a stand mixer, mix the melted butter and sugars together until combined. Add the egg, egg yolk, and vanilla extract and mix until smooth. Slowly add the dry ingredients and mix on low, just until combined. Stir in the butterscotch chips.
Press half of the dough evenly into the prepared pan, smoothing the top with the spatula. Drizzle salted caramel sauce over the dough. Top with remaining dough and evenly spread out using a spatula. It's ok if some of the caramel sauce peeks through. Sprinkle blondies with sea salt.
Bake for 30-35 minutes or until the top of the bars are light golden brown and the edges start to pull away from the pan. Cool bars on a wire rack to room temperature. Cut blondies into squares and serve.
Note-these blondies are good served with vanilla ice cream and a drizzle of salted caramel sauce.