In a large mixing bowl, sift together the flour, sugar, baking soda, salt, cinnamon, nutmeg and orange zest. Stir in walnuts to coat them in the flour mixture.
In a medium bowl, stir together the bananas, yogurt, beaten eggs, cooled butter and vanilla extract.
Working gently, fold the banana mixture into the dry ingredients, just until completely mixed. The batter will be very thick and lumpy.
Scoop batter into prepared muffin tins (silpat or paper lined). It will make 12-15 muffins.
Bake for approximately 10-15 minutes, until muffins are golden brown and baked through the center.
Adapted from Sweet-Pea's Kitchen
Recipe by Just a Smidgen at https://justasmidgen.com/2012/01/17/understudied-orange-spice-banana-muffins/