In a medium bowl, whisk together flour, salt, baking powder, baking soda, and pumpkin pie spice. Set aside.
In a large bowl using a handheld electric mixer (or in the bowl of a stand mixer fitted with the paddle attachment), beat butter and sugar on low speed until blended. Add eggs one at a time, beating well after each addition.
Add pumpkin, mashed bananas, oil, and vanilla. Beat until combined, scraping bowl as needed.
Add flour mixture and mix on low until just combined. The batter will be thick.
Fill muffin cups completely full using an ice cream scoop or spoons. Divide cinnamon streusel topping evenly over the batter.
Bake 19-22 minutes, until toothpick comes out with a few moist crumbs.
Allow the muffins to cool for 10 minutes in the muffin pan before enjoying.