Watermelon BBQ Sauce

5-6 lb seedless watermelon, in chunks
8 oz tomato paste
1 Tbsp onion powder
1 Tbsp garlic powder
2 cup firmly packed brown sugar
1/2 cup sherry
2 tsp lemon juice
1 tsp liquid smoke

Cut the melon into pieces and place in a saucepan. Cook it uncovered over medium heat until the melon is the consistency of applesauce (approximately 2-3 hours). Stir it occasionally. Add remaining ingredients. Simmer uncovered over low heat for 2 hours. Allow to cool to room temperature before using.