Place the rice cereal squares into a large mixing bowl and set aside.

In a microwave-safe bowl, combine the white chocolate chips and unsalted butter. Microwave in 30-second increments, stirring after each, until the mixture is smooth and completely melted.

Whisk the lemon zest and lemon extract into the melted chocolate mixture until fully incorporated.

Pour the lemon-chocolate mixture over the cereal and use a rubber spatula to gently fold until all cereal pieces are evenly coated.

Add the powdered sugar to a large gallon-sized resealable plastic bag.

Transfer the coated cereal into the bag, seal it, and shake vigorously until the cereal is uniformly covered in powdered sugar.

Spread the mixture out onto a parchment-lined baking sheet in a single layer to cool and set for approximately 30 minutes before serving.