Step 1: Make the Raspberry Sauce
In a medium saucepan, combine the raspberries, sugar, and water.
Cook over medium heat, stirring occasionally, until the raspberries break down and the mixture thickens (about 5-7 minutes).
Remove from heat and let it cool slightly.
Step 2: Prepare the Brownie Batter
Preheat the oven to 350°F (175°C) and grease and line an 8x8-inch baking pan with parchment paper.
In a medium bowl, whisk together the melted butter and sugar until smooth.
Add the eggs and vanilla extract, mixing until combined.
Sift in the cocoa powder, flour, salt, and baking powder. Stir until just combined.
Pour the brownie batter into the prepared pan, spreading it evenly.
Step 3: Add the Raspberry Swirl
Drop spoonfuls of the raspberry sauce onto the brownie batter.
Use a knife or skewer to swirl the raspberry sauce into the batter, creating a marbled effect.
Step 4: Bake
Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the brownies to cool completely before cutting into squares.