Preheat your oven to 350°F (175°C). Line a 9x13 inch baking dish with parchment paper for easy removal later.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt.
In a large mixing bowl, combine the melted butter, brown sugar, and granulated sugar. Whisk until smooth and well blended.
Add the egg, egg yolk, and vanilla extract to the butter-sugar mixture. Whisk until creamy and homogeneous.
Gradually add the dry ingredients to the wet mixture, stirring gently with a spatula until just combined.
Gently fold in the butterscotch chips.
Pour the batter into the prepared baking dish. Use a spatula to spread it into an even layer.
Drizzle half of the salted caramel sauce over the batter and swirl it slightly into the batter.
Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown.
Once baked, let the blondies cool in the pan for about 15 minutes. Drizzle the remaining salted caramel over the top and sprinkle with sea salt before cutting into squares.