Jewel-like slabs of orange topped with a broiler-kissed meringue are as delicately delicious as they are beautiful to behold.
Preheat boiler. Slice peeled oranges into crosswise rounds. Zest and juice remaining orange into 2 separate small bowls and set aside. Whisk honey, salt, and egg whites in the bowl of an electric mixer set over a pot of simmering water until honey is dissolved and mixture is hot to the touch. Remove from heat and whisk in electric mixer on high speed until shiny, stiff peaks form, about 7 minutes. Add vanilla and whisk until just combined.
Divide meringue among 6 shallow oven-proof dishes, fashioning dollops with a spoon. Transfer dishes to a rimmed baking sheet and broil until meringue is just toasted, about 1 minute. Remove and set alongside citrus rounds, drizzling with juice and sprinkling with zest. Serve immediately.