Coat an 8-inch round cake pan with cooking spray and set it aside.

In a medium saucepan over medium-low heat, melt the butter. Once melted, add the marshmallows and cook, stirring constantly, until melted. Stir in the vanilla extract and then add the Rice Krispies cereal until well coated.

Transfer the mixture into the prepared cake pan and press it firmly against the inside edge to form about a 1-inch crust. Let it cool while preparing the filling.

In a medium saucepan over medium-low heat, melt the butter and pumpkin pie spice. Once melted, add the marshmallows and cook, stirring constantly, until melted. Stir in the orange food coloring, then add the Rice Krispies cereal until well coated.

Press the filling mixture firmly inside the crust border, compacting it. Allow it to cool completely in the pan.

Once cooled, place a serving plate on top of the pan and invert it. Slice the pie into wedges and top with a dollop of whipped cream if desired.