Preheat the oven to 325 degrees F, and mist a 9 by 13-inch pan with non-stick spray. Line with parchment.
Place the sugar, butter, and cocoa in a large microwave-safe bowl, and microwave* in one-minute increments, stirring, until the butter is completely melted and the mixture feels very warm to the touch.
Add the eggs, one at a time, stirring after each addition.
Stir in the vanilla.
Stir in the flour, baking powder, and salt.
Transfer half the batter to the pan, then drizzle with about 1/3 of the salted caramel.
Top with remaining brownie batter, and swirl about 1/3 of the salted caramel mixture on top.
Bake for 45-60 minutes, or until set around the edges but still soft towards the middle.
Cool completely in the pan, then transfer to a cutting board and cut into squares.
Drizzle with remaining caramel and garnish with sea salt.