Preheat the oven to 400° F. Line a 12-cup muffin tin with paper liners or lightly grease with butter or non-stick cooking spray. Set aside.
In a large mixing bowl, whisk together the pumpkin and egg until completely combined. Whisk in the vanilla, orange zest (if using), spices, and salt.
Add the oil, molasses, and milk, stirring until completely combined after each addition. Add the sugars, and stir to combine.
Add the baking powder and baking soda, and stir to combine. Fold in the flour until just mixed. Do not overmix.
Use a cookie scoop to divide the batter evenly between the muffin cups, filling each about 3/4 full.
Bake for 10 minutes at 400° F. Turn the oven temperature down to 375° F., and bake for an additional 7-9 minutes, until the muffin tops are set, and a cake tester inserted into the center of each muffin comes out clean.
Let cool in the muffin tin for 5-10 minutes, then transfer to a baking rack to cool completely. Serve warm or at room-temperature.