Measure and chop fresh watermelon into small, uniform pieces, and set aside.
1 cup fresh watermelon, chopped
Preheat the oven to 350°F (175°C). Line a cupcake tin with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking soda, and salt until well combined.
1 1/2 cups all-purpose flour, 1/2 cup granulated sugar, 1/2 teaspoon baking soda, 1/4 teaspoon salt
In a separate bowl, beat the eggs, melted butter, and vanilla extract until blended.
1/2 cup unsalted butter, melted, 2 eggs, 1 teaspoon vanilla extract
Pour the wet ingredients into the dry ingredients, stirring gently until just combined. Fold in the chopped watermelon pieces, ensuring even distribution without overmixing.
1 cup fresh watermelon, chopped, 1/2 cup unsalted butter, melted, 2 eggs, 1 teaspoon vanilla extract
Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 22-25 minutes or until a toothpick inserted into the center comes out clean, and the cupcakes are golden brown with slightly domed tops. The watermelon pieces should be tender and the batter moist.