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

In a large bowl, whisk together the canned pumpkin puree, melted butter, granulated sugar, large egg, and vanilla extract until smooth.

In a separate bowl, combine all-purpose flour, baking soda, baking powder, salt, and ground cinnamon.

Add the dry ingredients to the wet mixture and stir gently until just combined.

In a small bowl, mix melted butter, brown sugar, and cinnamon until smooth to create the swirl.

Spoon the batter into muffin cups halfway full and drizzle the cinnamon mixture over each.

Swirl the cinnamon mixture into the batter using a skewer or toothpick.

Bake for 20-25 minutes, until a toothpick inserted comes out clean.

Cool in the pan for 5 minutes, then transfer to a wire rack. Prepare the glaze by mixing powdered sugar, vanilla extract, and milk until smooth and drizzle over muffins.