Watermelon Sorbet

I bought a big watermelon on sale this weekend, and wanted to try something beyond watching it drip down my kids' arms eating wedges on the deck. We saved half of it for that messy fun, but we used the other half to make this sorbet. This was easy to make and fun for the kids to take part in making. They gobbled it up for dessert tonight, and my husband took a second serving after they were in bed for the night.
4 C watermelon puree (about 6 cups of cubed watermelon)
1/4 cup sugar
1 lime, zested
Pinch salt
1/2 cup sweetened condensed milk 
 Puree the watermelon. In a large pot, combine 1 cup of watermelon puree with sugar and lime zest. Simmer over medium-low heat, stirring until the sugar dissolves. Add salt, remaining 3 cups watermelon puree. Stir in sweetened condensed milk until incorporated. Pour mixture into a cake pan and freeze until firm. (Suggestion was for 4 hours or overnight)
Once firm, remove from freezer. Let soften at room temperature for several minutes before using a butter knife to cut in to 2-inch chunks. In batches in a food processor, pulse chunks until a smooth mixture forms. Transfer to a metal mixing bowl. Pack watermelon mixture tightly by placing a piece of plastic wrap directly on top of it and pressing down. Seal well for storage in the freezer. (Original recipe states that it may be stored up to one week)