In a 2-quart microwave-safe bowl, combine sugar and corn syrup. Heat, uncovered, on high for 3 minutes; stir. Heat 2 1/4 minutes longer.
Stir in peanuts, butter and cinnamon. Microwave, uncovered on high for 20 to 30 seconds or until mixture turns a light amber color (mixture will be very hot).
Quickly stir in baking soda and vanilla until light and foamy. Immediately pour onto a well-greased baking sheet and spread with forks.
Refrigerate for 20 minutes or until firm; break into small pieces. Store in an airtight container. Makes 1 1/4 pounds.
Notes
Note: This recipe tested on a 1,100 watt microwave.