Prepare the watermelon by cutting it into wedges, removing seeds, and blending into smooth juice. Aim for about 1 cup of watermelon juice.

In a large mixing bowl, sift together 1 cup of glutinous rice flour and ¼ cup of sugar until well combined.

Gradually pour the watermelon juice into the dry mixture, stirring until a smooth batter forms. Adjust juice as necessary for consistency.

Transfer the batter to a microwave-safe bowl, cover loosely with plastic wrap, and microwave in 30-second intervals for 2-3 minutes until sticky and slightly translucent.

Add 1 tablespoon of butter and mix until fully integrated. Ensure butter melts completely.

Dust hands and working surface with cornstarch. Knead the dough gently for 2-3 minutes until smooth and elastic.

Divide the dough into small portions, shape into discs ¼ inch thick, and refrigerate for at least 1 hour.

Dust the chilled discs with cornstarch before cutting into bite-sized pieces and serve.