Place 1 scoop ice cream in each of 4 dessert dishes; put into freezer.
Just before serving, peel bananas; cut lengthwise into halves. If
using regular bananas, cut each half crosswise into thirds.
butter in a 10-inch skillet over medium-high heat. Stir in piloncillo;
add orange juice and lime juice. Cook, stirring frequently, until
sauce is thick and syrupy, 6 to 8 minutes.
Add bananas to sauce;
cook, turning gently, just to heat through and coat with sauce,
about 1 minute. Gently stir in liqueur. Remove from heat.
Heat rum in small saucepan over low heat just until barely warm
to touch, about 30 seconds; do not allow to bubble. Pour rum over
hot banana mixture; immediately ignite with long match. Stir with
long-handled spoon until flames subside.
Place warm bananas around ice cream; spoon sauce over top.