Scatter half of the chopped onion in the bottom of a serving bowl. Add half of the crabmeat. Layer remaining onion followed by remaining crabmeat.
Combine canola oil, cider vinegar, salt, pepper, and cayenne and whisk thoroughly. Pour over the crabmeat and onion mixture, followed by the ice water. Press mixture down gently with a spoon. Cover and refrigerate for 2 hours or up to 24 hours.
Serve on a pile of butter lettuce with saltine crackers. Garnish with sliced lemons and oranges, if desired.
*Lisa serves over lettuce with tomato, avocado, blanched asparagus spears and/or hearts of palm.
Recipe and Image Source: kitchn