Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan and line the bottom with parchment paper for easy removal.
In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until well combined.
Add the eggs one at a time, whisking well after each addition. Stir in the vanilla extract.
In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients into the wet mixture, folding gently until just combined. Do not overmix.
Fold in the chopped pecans and chocolate chips until evenly distributed throughout the batter.
Spread half of the brownie batter into the prepared baking pan, smoothing it out evenly.
Drizzle half of the caramel sauce over the brownie layer.
Spoon the remaining brownie batter over the caramel layer, and then drizzle the rest of the caramel sauce on top. Using a toothpick, gently swirl the caramel into the brownie batter for a marbled effect.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Once baked, let the brownies cool in the pan on a wire rack for at least 30 minutes before cutting them into squares.
Notes
Serve warm with vanilla ice cream and extra caramel sauce for an indulgent treat.