01 - Line an 8x8 inch baking pan with parchment paper and lightly grease the surface to prevent sticking.
02 - In a small saucepan, combine watermelon puree, corn syrup, and lemon juice. Stir until thoroughly mixed.
03 - Sprinkle gelatin powder evenly over the fruit mixture. Let stand for 5 minutes to allow the gelatin to absorb liquid and bloom.
04 - Add granulated sugar to the saucepan. Heat over medium-low heat, stirring continuously until both gelatin and sugar completely dissolve. Do not let the mixture boil.
05 - Pour the hot liquid into the prepared baking pan. Use a spatula to smooth the surface evenly. Let cool at room temperature for 30 minutes.
06 - Transfer the pan to the refrigerator. Chill uncovered for 2 hours or until the candy is firm and completely set.
07 - While the chills set, combine 1/3 cup granulated sugar and citric acid in a small bowl. Mix well to distribute evenly.
08 - Remove the set candy from the pan. Cut into small squares using a sharp knife. Roll each piece in the sour sugar mixture until evenly coated on all sides.
09 - Place finished chews in an airtight container, separating layers with wax paper to prevent sticking. Store at room temperature for up to one week.