Watermelon has so much more to offer than just a refreshing summertime snack. And the entire watermelon can be used -- no need to throw away the rind. The juice adds the perfect amount of sweetness to a tangy BBQ sauce and the rind can be quickly pickled while the sauce cooks. Serve with chicken, ribs, vegetables or even stir the sauce into homemade baked beans for your next cookout and guests will be begging for the recipe.
Use a Y-shaped peeler to remove the outer green part of the watermelon. Scoop out the pink flesh and place in a blender (you should have about 1 pound 2 ounces); set the rind aside.
Blend the watermelon flesh in a blender until it becomes juice. Pour through a fine-mesh sieve into a medium saucepan. (The amount of juice you have will vary depending on the watermelon.) You will need 2 cups of juice in the saucepan; transfer any excess to an airtight container and refrigerate for up to 1 week and save for another use.
Add the ketchup, Dijon, Worcestershire, molasses, coriander, garlic powder, onion powder, 1/4 cup of the light brown sugar, 1/4 cup of the vinegar, juice of 1 lime and a generous amount of freshly ground black pepper to the saucepan and whisk until smooth. Bring to a boil over medium-high heat, stirring occasionally, then reduce the heat to medium-low and simmer, stirring occasionally, until the sauce has thickened and reduced by a quarter, about 20 minutes.
Meanwhile, combine the salt, lime zest, juice of the remaining lime, and the remaining 1/4 cup each light brown sugar and vinegar in a small saucepan and bring to a boil over medium-high heat. Cook, stirring once or twice, until the sugar has dissolved, about 5 minutes. Remove from the heat.
Cut the rind into 2-by-1/4-inch sticks; transfer to the small saucepan with the brine and stir to combine. Add the ice cubes (and stir until the ice has melted. Let sit for 5 minutes to quickly pickle. Drain the pickled rinds and transfer to a serving bowl.