With a thin sharp knife, cut the tops and bottoms crosswise off the oranges and lemons to expose the flesh. Stand an orange on the work surface and, working from top to bottom, carefully cut off the peel and white pith in wide strips, leaving the orange flesh intact.

Then, holding the orange over a bowl to catch the juice, cut between the membranes to release the orange sections.

Drop the sections into the bowl of juice. Squeeze the membranes to extract the juice and discard the membranes. Repeat with the remaining oranges and lemons.

Season the juice lightly with salt and white pepper. Add the olive oil and toss gently. Set aside until ready to serve.

You can make the sauce up to 2 hours ahead.