Turn on broiler. Toss the apples with the lemon juice, butter, and all but 2 tablespoons of the sugar. (Can be made to this point up to 1 day ahead. Store in a resealable plastic bag and refrigerate.) Arrange on a baking sheet in a single layer.
Broil the apples about 8 inches from the heat for 8 to 10 minutes or until tender. Sprinkle with the remaining 2 tablespoons of sugar and broil until melted.
Meanwhile, heat the rum or maple syrup in a small saucepan over low heat.
Serve the apples warm with vanilla ice cream. Drizzle with the warm rum or syrup.
To fake it...and save 20 minutes:Heat broiler. Dump the apples from two 12-ounce packages scalloped apples onto a broiler pan or baking sheet. Toss with the grated zest from 1 lemon. Spread the apples in a single layer and broil about 8 inches from the heat for 5 minutes or until bubbly. Meanwhile, heat 1/3 cup rum or 1/2 cup maple syrup in a small saucepan over low heat. Serve the apples warm with vanilla ice cream. Drizzle with the rum or syrup. Total time: 10 minutes.