Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.
In a large bowl, whisk together the pumpkin puree, sugar, vegetable oil, and eggs until smooth.
In another bowl, mix the flour, baking powder, cinnamon, nutmeg, and salt. Gradually add the dry ingredients to the wet ingredients and mix until just combined.
Divide the batter evenly among the muffin cups, filling each about ⅔ full.
For the crumb topping, combine the brown sugar, flour, melted butter, and cinnamon in a small bowl. Mix until crumbly and sprinkle over the muffin batter.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.