This icy treat is inspired by good old-fashioned lemon meringue pie.
Divide sherbet among four 6-ounce ramekins or custard cups; cover with plastic wrap, and freeze until very firm, at least 2 hours.
Preheat oven to 475 degrees. With an electric mixer, beat egg whites with a pinch of salt on medium-high speed until soft peaks form. With mixer on low speed, gradually add sugar (about 1 tablespoon every 20 seconds); continue beating until peaks are stiff and glossy.
With a flexible spatula, mound meringue on sherbet; swirl and spread to edges of ramekins with the back of a spoon. Place on a baking sheet; bake until meringue is golden, 2 to 3 minutes. Serve immediately.
To assemble the parfaits ahead of time, fill ramekins with sherbet (no need to freeze at this point); then top with meringue. Freeze (uncovered) at least 2 hours and up to overnight. Bake as directed just before serving.