Preheat the oven to 350F. Prepare a muffin tin with muffin liners.
In a stand mixer with paddle attachment, cream together the sugar and butter until smooth.
Add the egg one at a time while scraping the bowl in between. Add the vanilla extract.
Add the yogurt and mix to combine. Combine the dries and add it to the mixer in two to three additions.
Fold in the bananas and walnuts.
Scoop the batter into the prepared muffin tin. Sprinkle turbinado sugar on top and bake for 20-25 minutes. It should be golden brown and firm to the touch.