Preheat oven to 350 F. Line a baking sheet with parchment paper or spray with cooking spray.
Beat together I Can't Believe It's Not Butter!® spread, brown sugar and granulated sugar. Add vanilla and egg and mix well. Mix in pumpkin puree.
In a separate bowl whisk together flour, salt, cinnamon and baking powder.
Add dry ingredients to wet ingredients and mix until dough comes together.
Roll dough into 1 inch balls and place on baking sheet. Gently flatten each cookie dough ball.
Bake for 10-13 minutes until cookies are golden brown.
Immediately after removing from the oven, use your thumb or the end of a wooden spoon (or similar object) to gently press an indentation into the center of the cookie. Allow the cookies to cool completely.
Meanwhile make the frosting. In a small bowl, mix together 1/4 cup I Can't Believe It's Not Butter!® spread, powdered sugar, and rum. Spoon teaspoonfuls of frosting into the center indentation of each cookie. Sprinkle with nutmeg.