Stir together the lime zest and juice, sugar and pepper. Add the watermelon, basil, cucumber, jalapeno and onion and toss gently. Chill the salsa until ready to serve.
Add the garlic salt just before serving. Serve with tortilla or pita chips.
Adapted from "Home Cooking with Trisha Yearwood" by Trisha Yearwood © Clarkson Potter 2010. Provided courtesy of Trisha Yearwood. All rights reserved.