Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or line it with parchment paper for easy removal.

In a saucepan over medium heat, melt the butter completely. Once melted, remove it from the heat and stir in the granulated sugar until well combined.

Let the butter mixture cool slightly, then add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, cocoa powder, and salt. Gradually add these dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix!

In a small bowl, take half of the caramel sauce and set it aside. The other half will be swirled into the brownie batter.

Pour the brownie batter into the prepared pan and then drizzle the caramel sauce over the top. Using a knife or a toothpick, gently swirl the caramel into the brownie batter to create a marbled effect.

Place the pan in the preheated oven and bake for 25-30 minutes or until a toothpick inserted into the center comes out with moist crumbs (not wet batter).

Once baked, remove from the oven and allow the brownies to cool completely in the pan before cutting them into squares. Drizzle the reserved caramel sauce over the top just before serving, if desired.