For a tangier twist, swap in oranges or grapefruit for the cantaloupe.
In small pan, heat oil over medium. Add shallot; cook until golden, 3 to 4 minutes. Remove with slotted spoon to paper towels; season. Pour reserved oil into a bowl and whisk in vinegar; season. On a platter, arrange remaining ingredients; season. Top with dressing, shallots, and fronds.