Grease bottom and sides of 8-inch square pan with butter or cooking spray. Place cereal in resealable food-storage plastic bag; seal bag and slightly crush with rolling pin or flat side of meat mallet (or slightly crush in food processor).
In large bowl, mix cereal and sunflower nuts; set aside.
In 3-quart saucepan, heat honey, 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.
Press mixture evenly into pan with back of wooden spoon. Refrigerate about 1 hour or until set. Cut into 4 rows by 4 rows. Store covered at room temperature.