Preheat oven to 350°F (175°C) and grease your donut pan.
In a large bowl, whisk together 1 cup + 1/4 cups flour, 1/2 cup light brown sugar, 1/2 teaspoon salt, 1 teaspoon baking powder, and 3/4 teaspoon pumpkin spice.
In another bowl, combine 1/4 cup pumpkin pie puree, 2 1/2 tablespoons melted unsalted butter, and 1/2 cup milk until smooth.
Pour wet ingredients into dry ingredients and mix gently until just combined.
Fill the donut pan cavities about three-quarters full with batter.
Bake for approximately 12 minutes or until a toothpick comes out clean.
Let cool slightly before brushing with melted butter and rolling in cinnamon sugar.