Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper, leaving some overhang for easy removal later.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Beat in the eggs one at a time, followed by the vanilla extract until well combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing just until combined.
Reserve 1 cup of the batter and spread the remaining batter evenly into the prepared baking pan.
Drizzle the caramel sauce generously over the batter layer, then gently dollop the reserved batter on top in spoonfuls, leaving some caramel exposed.
Bake in the preheated oven for about 25-30 minutes or until the top is golden brown and a toothpick inserted comes out with a few moist crumbs.
As soon as you remove the bars from the oven, sprinkle the sea salt over the top for a delightful contrast.
Allow to cool completely in the pan on a wire rack, then lift out using the parchment overhang and cut into squares.
Notes
Serve in a rustic wooden tray and drizzle more caramel sauce on top for extra decadence.