1Butter bottom and sides of 8-inch square pan, or spray with cooking spray. Place cereal in resealable food-storage plastic bag; seal bag and slightly crush with rolling pin or meat mallet (or slightly crush in food processor).
2In large bowl, mix cereal and sunflower nuts; set aside.
3In 3-quart saucepan, heat corn syrup, brown sugar, apples and cinnamon just to boiling over medium-high heat, stirring occasionally. Remove from heat; stir in peanut butter. Pour over cereal mixture; stir gently until evenly coated.
4Press mixture evenly into pan with back of wooden spoon. Refrigerate about 1 hour or until set. For bars, cut into 4 rows by 4 rows. Store covered at room temperature.