Cut the papaya in half lengthwise. Scoop out the seeds, put them in a strainer, and rinse. Cover the papaya in plastic wrap and reserve. Arrange the seeds on a baking sheet and bake in a 350F oven, turning twice, for 15 minutes. Do not overbake or they will become tasteless. Cook and dry.

Place seeds in a mortar and crush with a pestle to a coarse grind (or use the bottom of a heavy skillet) so you get at least 1 tablespoon.

In a bowl, dissolve the sugar in the oil, lime juice, and salt. Add the hearts of palm and mix.

Arrange the lettuce on a serving plate. Slice the reserved papaya and place the slices attractively over the lettuce. Mound the hearts of palm and dressing in the center of the plate. Cover with onion slices and sprinkle with the crushed papaya seeds.