Preheat the oven to 350 degrees F (175 degrees C). Grease a rectangular cake pan.

Blend together quinoa, melted butter, eggs, milk, and vanilla in a blender until smooth.

Combine sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl. Stir quinoa mixture into sugar mixture until batter is well combined. Fold in chocolate chips and pecans until incorporated. Pour into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center of cake comes out clean, 40 to 45 minutes. Place on a wire rack to cool completely.