Preheat your oven to 325°F (160°C) and grease an 8-inch square baking pan or line it with parchment paper.

In a medium bowl, whisk together the flour, baking soda, and salt.

In a large bowl, beat the butter until smooth, then add the granulated sugar and brown sugar and mix until fluffy.

Add the egg, vanilla extract, and sour cream to the butter and sugar mixture, and beat until combined.

Gradually mix the dry ingredients into the wet ingredients just until combined, then divide the dough in half.

To one half, sift in the cocoa powder and mix until fully incorporated.

Spoon the chocolate dough into the prepared pan, then add the vanilla dough on top and spread gently.

Bake for 35-40 minutes or until golden brown and a toothpick comes out clean.

Allow the bars to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

Prepare the raspberry glaze by smashing the raspberries and mixing the juice with confectioner's sugar until smooth.

Once the bars are cool, pour the raspberry glaze on top and allow it to set before slicing into squares.