Begin by gathering all necessary ingredients. Preheat your oven to 350°F (175°C). Prepare 14 muffin cups by greasing them with cooking spray or lining them with paper liners that have also been sprayed.
In a large mixing bowl, combine the pumpkin puree, melted butter, brown sugar, water, eggs, and vanilla extract. Stir the mixture until well blended.
In a separate bowl, whisk together the all-purpose flour, white sugar, pumpkin pie spice, salt, baking soda, ground cinnamon, and baking powder. Gradually add this dry mixture to the pumpkin mixture, stirring until everything is fully incorporated.
Spoon the batter into the prepared muffin cups, filling each about three-quarters full.
Bake in the preheated oven for approximately 25 to 30 minutes, or until the muffins are slightly browned on top and spring back when gently pressed.
