Place the Chex cereal in a large mixing bowl and set it aside.
In a separate microwave-safe bowl, combine the white chocolate chips, unsalted butter, lemon zest, and lemon juice.
Microwave the mixture for 1 minute.
Remove the bowl from the microwave and stir the mixture thoroughly.
Continue microwaving in 30-second intervals, stirring well after each interval, until the white chocolate and butter are fully melted and smooth.
Pour the melted lemon white chocolate mixture over the Chex cereal.
Stir gently with a spatula or large spoon until the cereal is evenly coated. Avoid crushing the cereal while mixing.
Transfer the coated cereal to a large ziplock bag.
Add the powdered sugar and salt to the bag.
Seal the bag securely.
Shake the bag until the cereal is completely coated with the powdered sugar mixture.
Transfer the Lemonade Puppy Chow to a serving bowl.
Serve immediately, or store in an airtight container until ready to serve.