Blend the watermelon flesh in a blender or food processor until smooth. Strain to remove excess liquid if necessary, then measure out 1 cup of the puree and set aside.
1 cup watermelon flesh
Preheat the oven to 350°F (175°C). Line a cupcake pan with paper liners. In a small bowl, combine the sugar and 1/4 cup of the watermelon puree to create a sweetening mixture.
1 cup watermelon flesh
In a large mixing bowl, whisk together the flour, baking powder, baking soda, and salt until evenly combined. In a separate bowl, whisk the eggs, vegetable oil, vanilla extract, and the remaining watermelon puree until well incorporated.
1 cup watermelon flesh
Gradually add the wet mixture into the dry ingredients, folding gently with a spatula or spoon until just combined. Do not overmix to keep the batter light and airy.
1 cup watermelon flesh
Spoon the batter evenly into cupcake liners, filling each about two-thirds full. Sprinkle a little extra sugar on top of each cupcake for a sugary crust.
1 cup watermelon flesh
Bake in the preheated oven for 20-25 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean. Once baked, remove from the oven and cool on a wire rack until completely cooled.
