Drain cherries, reserving juice. Add water, if needed, to make 1⅓ c. juice.
Combine sugar, cornstarch and salt in saucepan; gradually stir in cherry juice. Cook mixture, stirring constantly, over medium heat until it boils and is thickened and clear, about 6 minutes.
Add butter, stirring until it melts, and a few drops of red food color. Stir ½ c. drain