7 tangerines or oranges (do not peel), preferably organic, washed well, quartered, and sliced 1/4 inch thick
2 lemons (do not peel), preferably organic, washed well, quartered, and sliced 1/4 inch thick
4 cups water
Bring tangerines, lemons, and water to a simmer in a large saucepan over medium heat. Cook for 5 minutes. Let cool slightly. Press parchment directly on surface of marmalade, and refrigerate overnight.
Remove parchment; return saucepan to medium heat. Bring to a simmer, and cook until citrus rinds are very tender, about 30 minutes. Measure mixture, and return to saucepan over medium-high heat. For each cup of mixture, add 3/4 cup sugar. Simmer until a candy thermometer registers 220, about 30 minutes. (Tangerine and lemon flesh should be broken down, and rinds should be translucent.) Plate-test marmalade to make sure it is set. Divide among 4 pint-size sterilized glass jars, leaving 1/4-inch headspace at tops. Can in water bath for 15 minutes.