With a zester or vegetable peeler, remove the zest (colored peel only) from half of an orange. Finely mince the zest and transfer it to a large stainless steel or glass bowl. Add the salsa and lime juice to the orange zest. Taste and season with salt (should be a little salty). Add the jicama and onion, toss to mix well, then let stand for about 30 minutes.
Cut the stem and blossom ends from all the oranges, then standing each orange on a cutting board and working close to the flesh, cut away the rind and all the white pith. Cut the oranges into 1/4-inch-thick slices. Cut the slices into quarters.
Stir the orange pieces and optional pineapple into the jicama mixture. Divide the lettuce between individual serving plates, forming it into a rough nest shape. Pile the marinated jicama mixture in the middle. Sprinkle everything with cilantro