Sweet and Spicy Watermelon Sauce
Watermelon flesh and pink/white rind but don't use any of the bright white or bitter green
1 1/4 c brown sugar (or white sugar and 1 heaping T molasses)
3-4 T water
1/4 t cream of tartar
dash of salt
1/4 c ketchup (reduced sugar is fine too)
1/4 c white vinegar
3/4 t crushed red pepper flakes
1/2 t liquid smoke flavor (hickory or mesquite)
1/8 t ground black pepper 
Chop watermelon and pink/white rind into chunks.  About 3 cups full of 
chunks.  Place in a food processor and pulse briefly to puree.  You want
 about a cup full more or less and you want it to stay thick.
To a saucepan on the stove place the brown sugar (or white sugar with 
molasses added) into a pan.  Add the cream of tartar, dash of salt and 
about 3-4 T water.  I used a mixture of white and brown sugar but found I
 was out of molasses. No worries, you are just making a general syrup.  
Bring to a boil, reduce heat and simmer about 3 or 4 minutes until it's 
thickened. Add the watermelon puree, ketchup, vinegar, red pepper 
flakes, flavoring and pepper.  If you want to use less crushed red 
pepper flakes you can, or substitute similar measurements of minced 
jalapeno, canned green chilies, or for a completely sweet sauce, leave 
out the spice.  Bring to a boil again, reduce to s simmer and let simmer
 for 1-2 hours until it reduces down, becomes dark and thickens.  The 
longer you simmer, the thicker and darker it becomes.
I canned mine in sterilized jars with lids and used a water bath process
 for 30 minutes.  But then we ended up using it that night anyway 
because it was SO good I couldn't wait!  We used it on grilled chicken 
(basted, grilled, basted more, grilled more and finally, final basted 
and served extra with dinner).   We are saving the rest to use with 
Cream Cheese Won Tons like a spicy, sweet plum sauce.
  | 
| Making a simple syrup | 
  | 
| Cleaning the watermelon | 
  | 
| Scraped and chopped. You can use these rinds for watermelon pickles or discard. | 
  | 
| Pureed watermelon and the pink/white part of the rind | 
  
  | 
| Bringing to a boil | 
  | 
| /Simmer until it's as thick as you need or want it to be |