Preheat the oven to 350°F (175°C) and line a cupcake pan with paper liners.
Blend fresh seedless watermelon until smooth to make about 1 cup of puree. Measure out and set aside.
In a large mixing bowl, whisk together the softened melted butter and sugar until well combined and slightly fluffy.
Add eggs one at a time to the butter mixture, whisking after each addition until fully incorporated.
Stir in the vanilla extract and watermelon puree, mixing until the batter is smooth and evenly colored.
In a separate bowl, sift together the flour, baking powder, baking soda, and salt.
Gradually fold the dry ingredients into the wet mixture using a spatula, mixing just until combined. Do not overmix.
Gently fold in the finely chopped watermelon chunks, distributing them evenly throughout the batter.
Spoon the batter into the prepared cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean and the tops are lightly golden.
Let the cupcakes cool in the pan for 5 minutes, then transfer to a cooling rack to cool completely before serving.
Enjoy these vibrant, fruity cupcakes as a refreshing summer treat, showcasing the juicy texture of watermelon.
