Very difficult to bake with watermelon, as it's almost all water.
If you want fruit flavor in baking without a lot of liquid, use a fruit juice concentrate or syrup (and adjust the sugar accordingly).
Have a look at this selection of recipes for watermelon concentrates or syrups and see if one or more gives you what you want in terms of taste or texture.
https://www.google.ca/search?q=watermelon+concentrate+recipe&oq=watermelon+concentrate+recipe&aqs=chrome..69i57.5044j0j7&sourceid=chrome&ie=UTF-8
3 Comments
If you want fruit flavor in baking without a lot of liquid, use a fruit juice concentrate or syrup (and adjust the sugar accordingly).
https://www.google.ca/search?q=watermelon+concentrate+recipe&oq=watermelon+concentrate+recipe&aqs=chrome..69i57.5044j0j7&sourceid=chrome&ie=UTF-8