1. Preheat your oven to 350°F (175°C) and line a 9×13 inch baking pan with parchment paper, leaving an overhang on the sides.
2. In a microwave-safe bowl, melt the butter, then stir in the sugar until well combined. Allow the mixture to cool slightly.
3. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
4. In a separate bowl, whisk together the flour, cocoa powder, salt, and baking powder. Gradually add this dry mixture to the butter mixture, stirring until just combined.
5. Fold in the chopped pecans, reserving a few for the top if desired.
6. Pour half of the brownie batter into the prepared pan and spread evenly. Drizzle half of the caramel sauce over the batter, then spread the remaining brownie batter on top.
7. Swirl the remaining caramel sauce over the top and sprinkle with sea salt flakes and reserved pecans.
8. Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs attached.
9. Allow the brownies to cool completely in the pan before lifting them out using the parchment overhang. Cut into squares and serve.

Remember, the key to these brownies is not to overbake them. They should have a slightly gooey center, ensuring that perfect fudgy texture we all love.