Heat butter in a microwave safe 4-cup measure or a medium microwave safe bowl on HIGH 1 minute or until melted.
Stir in brown sugar and pumpkin pie spice until well blended. Add nuts. Stir until evenly coated.
Microwave on HIGH 2 to 3 minutes, stirring at the end of each minute until mixture comes to a full boil. Carefully spread nuts on to a waxed paper or parchment lined baking sheet (nuts will be very hot). Allow to cool at least 10 minutes, serve warm or at room temperature.
Replace spices with 2 teaspoons pumpkin pie spice, if desired.