Put tomatoes, sugar, sliced lemon and cinnamon in large, heavy pot and bring to slow boil over medium-high heat, stirring occasionally. When foam rises to surface, add butter and continue stirring and simmering until preserves thicken, about 45 minutes. (To test, stick a fork into preserves. When preserves cling to tines of fork, it should be thick enough to can.) Pour preserves into sterilized jars, seal and process in hot water bath for 15 minutes.