First, start out by preheating the oven to 350 degrees.
In a large bowl, start by adding in the softened butter and both granulated sugar and brown sugar and beat the mixture so it's creamy.
Next, add in the vanilla extract, eggs, and Nutella and continue to beat mixture.
Following, add in all of the dry ingredients (cacao powder, salt, baking powder, and gluten-free all purpose flour). Blend everything until the mixture is smooth.
Add the bittersweet chocolate chips in and give it a quick stir.
Lastly, grease and flour an 8" square cake pan. Pour the batter in and bake for about 30 minutes.