01 - Line an 8x8 inch baking pan with parchment paper and lightly grease it to prevent sticking.
02 - In a small saucepan, combine watermelon puree, corn syrup, and lemon juice. Stir until thoroughly blended.
03 - Sprinkle gelatin powder evenly over the fruit mixture. Let stand for 5 minutes to allow the gelatin to hydrate and absorb the liquid.
04 - Add granulated sugar to the saucepan. Heat over medium-low heat, stirring continuously until gelatin and sugar completely dissolve. Do not allow the mixture to boil.
05 - Pour the hot mixture into the prepared pan. Use an offset spatula to smooth the surface. Let cool at room temperature for 30 minutes.
06 - Refrigerate uncovered for 2 hours or until the candy is completely set and firm to the touch.
07 - In a small bowl, whisk together 1/3 cup granulated sugar and citric acid powder until evenly combined.
08 - Cut the set candy into small squares using a sharp knife. Roll each piece in the sour sugar mixture, pressing gently to ensure even coating on all sides.
09 - Layer the finished chews in an airtight container with wax paper between layers to prevent sticking. Store at room temperature for up to one week.