10 TBS unsalted butter, room temperature, plus more for the pan
3 cups all-purpose flour (spooned and leveled) plus more for pan
2 1/2 tsp baking powder
1/4 tsp baking soda
1 tsp coarse salt
1/2 tsp ground nutmeg
1/4 tsp ground allspice
1/3 cup buttermilk
1 1/4 cups pure pumpkin puree (from a 15 oz can)
3/4 cup light-brown sugar
2 large eggs
Preheat oven to 350. Butter and flour 12 standard muffin cups.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, nutmeg, and allspice. In a small bowl, whisk together buttermilk and pumpkin puree. In a large bowl, using an electric mixer, beat butter and brown sugar until light and fluffy. Beat in eggs, one at a time, scraping down bowl as needed. With mixer on low, add flour mixture in three additions, alternating with two additions of pumpkin mixture, and beat to combine.
Spoon 1/3 cup batter into each muffin cup and bake until a toothpick inserted in center of muffin comes out clean - 30 minutes.
Sugar Coating
3/4 cup granulated sugar
2 1/2 tsp ground cinnamon
1/4 cup (1/2 stick) unsalted butter, melted
Combine sugar and cinnamon. Let muffins cool 10 minutes in pan on a wire rack. Working with one at a time, remove muffins from pan, brush all over with butter, then toss to coat in sugar mixture. Let muffins cool completely on a wire rack.