1. Slice 1 lemon. In a heavy-bottom stockpot, bring the lemon slices, allspice, onion powder, cayenne, salt, and 4 cups water to a boil. Reduce the heat and simmer for 15 minutes. Add the shrimp and poach for 3 to 4 minutes. Strain and shock the shrimp in ice water until completely cooled. Pat dry on paper towels.

2. Zest and juice the remaining lemon. (It should yield about 1 tablespoon of zest and 3 tablespoons of juice.)

3. In a large bowl, combine the poached shrimp, lemon zest and juice, olives, celery and celery leaves, parsley, and oil. Season with salt and pepper.

4. Fold in the hearts of palm, then transfer to a serving platter. Garnish with celery leaves, parsley, and black pepper and drizzle with oil.