Preheat oven to 400 degrees F (200 degrees C). Grease a 12-cup muffin tin.
Beat egg in a bowl. Stir in persimmon pulp, oil, and milk.
Combine flour, walnuts, sugar, salt, baking powder, and cinnamon in a separate bowl. Stir flour mixture into persimmon mixture; mix until just moistened. Fill muffin cups 3/4 full.
Bake in the preheated oven until golden brown and tops spring back when lightly touched, 19 to 20 minutes.
