Preheat your oven to 350°F (175°C). Grease a baking pan.
In a mixing bowl, combine melted butter and sugar. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
In another bowl, whisk together flour, cocoa powder, and salt. Gradually add to the wet ingredients, mixing until just combined.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool completely.
For the caramel sauce, heat sugar in a saucepan over medium heat, stirring constantly until it melts into a thick amber-colored liquid.
Add butter and stir until melted. Slowly pour in heavy cream while stirring. Allow the mixture to boil for 1 minute, then remove from heat and stir in sea salt.
Pour the caramel sauce over the cooled brownies. Let it set before cutting into bars.