01 - Line a large baking sheet with parchment or wax paper and set aside.
02 - Place the rice cereal squares in a large mixing bowl.
03 - Combine white chocolate chips and butter in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each, until smooth and fully melted, approximately 1 to 1 1/2 minutes total.
04 - Stir lemon juice and lemon zest into the melted chocolate mixture until fully incorporated.
05 - Pour the melted mixture over the cereal. Gently fold with a spatula until all pieces are evenly coated.
06 - Combine powdered sugar and instant lemonade mix in a large zip-top bag.
07 - Add the coated cereal to the bag. Seal and shake vigorously until all pieces are well-coated with the sugar mixture.
08 - Spread the puppy chow onto the prepared baking sheet to cool and set for approximately 10 minutes.