Preheat the oven to 350°F (175°C).
Lightly grease or line an 8x8 inch baking dish with parchment paper.
Combine the dry ingredients in a large bowl — cocoa powder, baking powder, baking soda, cinnamon, and protein powder (if using). Whisk together until evenly blended.
In a separate bowl, combine wet ingredients — pumpkin puree, nut butter, maple syrup, and vanilla extract. Mix until smooth.
Gradually add the wet mixture into the dry ingredients, stirring until just combined. Do not overmix.
Fold in the chocolate chips.
Pour the batter into the prepared baking dish and smooth the top with a spatula.
Bake for 20–25 minutes or until a toothpick inserted into the center comes out mostly clean.
Let brownies cool in the pan for 10 minutes before cutting into squares and serving.