If using fresh cherries, wash and pit them. If frozen, thaw slightly. Measure out all ingredients.
In a large skillet over medium heat, melt butter. Add sugar, orange zest, and orange juice. Stir until sugar dissolves and mixture bubbles (about 2 minutes).
Add cherries to skillet. Cook, stirring gently, until cherries soften and release juices, 5-7 minutes. Sauce will thicken slightly.
Remove skillet from heat. Pour in brandy or kirsch. Carefully ignite with long lighter or match (stand back, flames can rise high). Gently shake pan until flames die down (about 30 seconds). Return to low heat if needed to reduce sauce 1-2 minutes until glossy.
Scoop vanilla ice cream into bowls. Spoon warm cherries and sauce over ice cream. Serve immediately while hot.