Scoop ice cream into bowls and freeze. This can be done a few hours ahead of time.
In saucepan, combine your sugar and halved cherries over medium low heat. Add your lemon juice and cover. Cook for 3 minutes on low heat. Take off the cover, take the pan off the fire and add the rum.
To flambe, swirl the pan until the rum catches fire. It should subside in a few seconds, if not, turn off the heat and cover with a lid. The cover will help snuff out the flames.
Pour the cherries onto the frozen ice cream and enjoy immediately.