HEAT oven to 225 degrees F. Spray 15 x 10 x 1-inch baking sheet with no-stick cooking spray. Place popped popcorn in a very large bowl or Dutch oven.
COMBINE hazelnut spread, corn syrup, salt, cinnamon and cayenne pepper in a medium saucepan over medium heat, stirring constantly, until mixture begins to boil. Remove from heat.
POUR warm mixture over popcorn, stirring gently to combine. When all popcorn appears evenly coated, spread evenly on prepared baking sheet. Bake 55 to 60 minutes, stirring occasionally. Remove from oven and allow to cool. May be stored in airtight container for up to one week.