Preheat the oven to 350 degrees.
In a bowl, whisk together the 2 cups all purpose flour, 2 tsp baking powder, and 1 tsp salt.
2 cups all purpose flour, 1 ½ cups granulated sugar, 2 tsp baking powder, 1 tsp salt
In a separate bowl, whisk together the 1 ½ cups granulated sugar, ½ tbsp key lime zest, 2 tbsp key lime juice, and 1 ½ tsp vanilla extract until smooth. Add the 2 egg and 1 cup whole milk and stir to combine.
½ tbsp key lime zest, 2 tbsp key lime juice, 2 egg, 1 ½ tsp vanilla extract, 1 cup whole milk
Add the wet ingredients into the dry ingredients until a thick batter forms.
Fill a piping bag or a plastic bag with a 1-2 inch opening. Pipe the batter into a donut pan, filling each mold to the top.
Bake for 15-20 minutes until a toothpick inserted comes out clean.
In a food processor or spice grinder, add the 2 tbsp granulated sugar, 1 tsp sea salt, and 1 bag of freeze-dried watermelon. Blend until a fine powder is formed.
1 bag of freeze-dried watermelon, 2 tbsp granulated sugar, 1 tsp sea salt
As soon as the donuts come out of the oven, toss in the watermelon sugar. Place on a drying rack and cool for 30 minutes. Toss in the watermelon sugar an additional time before serving.