Puree the watermelon chunks in a blender until smooth, then strain through a fine mesh to extract 1 cup of watermelon juice. Set aside.
2 cups all-purpose flour
Preheat the oven to 350°F (175°C) and line a cupcake tin with paper liners.
In a large mixing bowl, combine the flour, baking powder, baking soda, and salt. Whisk together until evenly mixed.
In a separate bowl, beat the eggs with sugar and vegetable oil using an electric mixer until the mixture is smooth and slightly paler in color, about 2-3 minutes.
2 cups all-purpose flour
Gradually add the watermelon juice to the wet mixture, mixing until fully incorporated. Then, fold in the dry ingredients just until no streaks remain, avoiding overmixing.
2 cups all-purpose flour
Spoon the batter into the prepared cupcake liners, filling each about two-thirds full. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean and the tops are lightly golden. Allow cupcakes to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.