Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.

In a large mixing bowl, whisk together the pumpkin puree, sugar, vegetable oil, eggs, and vanilla extract until smooth.

In another bowl, combine the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

In a small bowl, mix together the flour, brown sugar, melted butter, cinnamon, and pecans until crumbly.

Scoop the muffin batter into the prepared muffin tin, filling each cup about 2/3 full.

Sprinkle the streusel topping evenly over each muffin.

Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.

Allow to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.