Begin by preheating your oven to 350°F (175°C).
Line your 9x9 inch baking pan with parchment paper.
In a microwave-safe bowl, melt the butter or coconut oil until completely liquid. Set aside to cool slightly.
In a mixing bowl, combine the melted butter or coconut oil, light brown sugar, natural sweetener, eggs, and vanilla extract. Whisk until smooth.
Pour the warmed Nutella into the wet mixture and whisk until fully incorporated.
In another bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry mixture to the wet mixture, stirring gently until just combined.
Using a spatula, gently fold in the raspberries, blueberries, and chocolate chips.
Pour the batter into the prepared baking pan, spreading it evenly. Bake for 25-30 minutes.
Once baked, remove from the oven and let cool for about 10 minutes before transferring to a wire rack.
