Preheat your oven to 350°F (175°C) and lightly grease an 8-inch or 9-inch oven-safe skillet.
Mash the ripe bananas in a large mixing bowl until mostly smooth.
Whisk in the eggs, honey or sugar-free syrup, and vanilla extract until fully combined.
Stir in the zero sugar yellow cake mix, vanilla protein powder, and cinnamon until just combined.
Gently fold in your chocolate chips or walnuts if using, saving a few for the top.
Spread the batter evenly into the prepared skillet and top with any remaining mix-ins.
Bake for 24 to 30 minutes, or until the center is set and a toothpick comes out mostly clean.
Let cool for at least 10 minutes before slicing into 8 pieces and serving.
