Drain the cherries, reserving the juice in a bowl. Mix the cornstarch into the cherry juice and heat in a skillet. Add the orange zest and cherries. Heat the rum in microwave for approximately 10 seconds, or in a small pan on top of the stove until warm. Add the rum to the cherry mixture and ignite with a match. Be very careful with this! Place one-half cup of ice cream in each of four bowls and spoon cherries over it.