Place 2 1/2 cups water in a large sauce pan. Add the cinnamon stick and the lemon peel. Bring to a boil, reduce heat to low, and simmer, uncovered for about 20 minutes. Remove lemon peel and cinnamon stick and discard. Reserve liquid!
While the cinnamon and lemon are simmering, cook the boniato. Place the peeled and quartered boniato in a large sauce pan and cover with water. Add one teaspoon salt. Bring to a boil, reduce heat to low, and simmer, covered until very tender -- about 30 minutes. Drain. Use an electric mixer or food processor to puree the cooked boniato until you have a very smooth paste.