Preheat oven to 400 °F and line a baking sheet with parchment paper or foil.
Place 2 sheets of thawed puff pastry on the baking sheet, slightly overlapping one over the other.
Arrange the sliced cantaloupe in the center of the puff pastry, creating two rows that overlap.
In a small mixing bowl, mix together butter, brown sugar, flour, and cinnamon.
Crumble the mixture over the cantaloupe evenly, then fold the sides of the puff pastry inwards.
Whisk the egg yolk and water together to create an egg wash. Brush over the edges of the puff pastry, then sprinkle raw sugar on top of the egg washed areas.
Bake in the oven for 18-20 minutes until the pastry is puffed and golden brown on the edges.