In a small Dutch oven, combine the strawberries, 1/2 cup water, lemon juice, and cinnamon. Stirring well, bring the mixture to a boil.
Dissolve the cornstarch in the remaining 1/4 cup water, and then stir it into the boiling mixture. Reduce the heat, and then continue to simmer for 2 to 3 minutes, stirring occasionally, until the mixture thickens.
Remove from the heat, and let cool. Stir in the sugar substitute.