Preheat oven to 350. Line muffin tin with parchment liners.
In a large mixing bowl, mash the bananas, then add the pumpkin puree, melted butter and maple syrup. Mix well using a whisk. Then add the remaining wet ingredients - eggs, vanilla and mix thoroughly until combined.
In another medium mixing bowl, combine the gluten free flour, protein powder, baking soda, baking powder, and spices until well incorporated.
Using a spatula, fold in the dry ingredients into the wet until just combined. Be sure not to over-mix.
If you haven’t already, line your muffin tin with parchment paper liners or spray. Fill each muffin liner with batter almost all the way - a large cookie scoop is usually the perfect measurement.
Once liners are filled with batter, make the streusel topping and top muffins liberally.
Ensure the oven is preheated to 350°F, place the pan on the middle rack in oven and bake for 18-22 minutes. You will know the muffins are done when a toothpick comes out mostly clean.Allow the muffins to cool in the baking tin for 5 minutes, then transfer to a wire rack to cool completely.