Preheat your oven to 350°F (175°C) and line an 8-inch baking pan with parchment paper.

In a saucepan, combine raspberries, sugar, and a splash of water. Cook over medium heat for 5-7 minutes until thickened, then strain to remove seeds.

In a clean saucepan, melt chocolate chips and butter over low heat. Stir for 4-5 minutes until smooth, then cool slightly.

Whisk together eggs, sugar, and vanilla extract until light and fluffy. Gradually mix in the cooled chocolate mixture.

Sift in flour, salt, baking powder, and baking soda. Gently fold until just combined.

Pour the batter into the prepared pan and dollop raspberry sauce on top. Swirl with a knife to create a marbled effect.

Bake for about 30 minutes until a toothpick inserted comes out with a few moist crumbs.

Cool completely in the pan on a wire rack before slicing into squares.