Preheat your oven to 350°F (175°C). Line or grease an 8x8-inch baking pan.

Melt ½ cup of unsalted butter in a microwave-safe bowl until completely melted. Allow to cool slightly.

Whisk in 1 cup of light brown sugar, then add 1 large egg, 1 teaspoon of vanilla extract, and 1 cup of pumpkin puree. Mix until smooth.

In a separate medium bowl, mix together 1 cup of all-purpose flour, 1 teaspoon of ground cinnamon, ½ teaspoon of ground ginger, ¼ teaspoon of ground nutmeg, 1 teaspoon of baking soda, and ½ teaspoon of fine sea salt. Whisk until even.

Fold the dry mixture into the wet mixture gently until no visible streaks of flour remain.

Pour the batter into the prepared baking pan and smooth the top. Bake for 25–30 minutes until a toothpick comes out clean.

Allow the bars to cool in the pan for 10 minutes before transferring to a wire rack.

In a medium bowl, beat together ¼ cup of softened unsalted butter and 1 cup of light brown sugar. Gradually add powdered sugar, ½ teaspoon of ground cinnamon, and 2–4 tablespoons of milk until desired consistency is achieved.

Once cooled, frost the bars with the brown sugar frosting and let it set before slicing.