Grease a 12-inch rectangular bread mold and cover with 2 large pieces of plastic wrap making sure they overlap so all the bottom and sides of the mold are covered and there is enough wrap on the sides of the mold so as to fold it once the causa has been assembled and you can tightly cover it. PREPARE THE RELISH: To start the relish, finely mince the red onion, place it in a bowl and cover it with the vinegar; allow to rest for about 45 minutes. POTATO PASTE: Place potatoes in a large pot with enough cold water to cover them by over 2 inches of water, add 2 tablespoons of salt and bring to a boil. Cook for about 25 minutes, until potatoes are tender when pierced with a knife. Drain and let them cool until you can handle them safely. Meanwhile, place the jalapeno pepper slices along with their juice in a blender and blend until smooth. Strain the mixture, separating the juice from pulp and keeping both. When the potatoes are cooled, peel them. Once they are peeled, press the potatoes through a potato ricer or the fine side of a cheese grater, making sure no lumps remain. Place potato paste in a large bowl and add the lime juice, canola or corn oil and 4 tablespoons of the jalapeno juice. Mix with a potato masher, adding salt and pepper to taste. Place in the refrigerator until cooled. TO COMPLETE THE RELISH: Strain the onion, discarding the vinegar; mix with the cilantro, a little bit of salt and pepper, 1/2 cup of the minced yellow peppers, the lime juice and 1 tablespoon of the jalapeno pulp (not the juice). Taste and check seasoning adding more salt, pepper, juice or paste if desired, according to preference. MAKE THE CAUSA: Mix the crabmeat with the mayonnaise and the lime juice; season with salt and pepper to taste. Place in refrigerator. Cut the avocado in half lengthwise, removing the pit. Cut each half in half again, making a total of four wedges. Using a large spoon, scoop each full avocado wedge out of the skin. Cut 1/4-inch thick slices across each avocado wedge (not lengthwise). Season with a little bit of salt, pepper and sprinkle some lime juice over all the slices. PREPARE THE TERRINE OR BREAD MOLD: Once the potato paste is cooled, use a large spoon to spread 1/3 of the paste into a layer at the bottom of the bread mold. Use the backside of the spoon to evenly coat all of the bottom. Place 1/2 of the avocado slices in the mold for the next layer - making sure all corners and sides of the mold are covered with avocado. Set aside six dollops of crabmeat mixture for the serving. Now place 1/2 of the remaining crabmeat mixture into the mold for the next layer. Press down firmly with the back of a spoon. Repeat with one layer each of potato paste, avocado and crab, and then finish with a layer of potato paste on top. Fold the plastic wrap over the top of the mold (use more plastic wrap if needed to seal the top well). Press slightly and put in the refrigerator to chill well, at least one hour. (Place the extra crabmeat mix into the refrigerator as well.). To serve, carefully uncover the plastic wrap from the top of the mold. Unmold the crab causa over a serving platter. Spread some of the relish over the top of the causa. Place chopped lettuce leaves on six serving plates. Cut the causa carefully into six slices and, using a spatula, lift each slice and place one slice on top of the lettuce on each serving plate. Add more of the relish on the top of each slice and a dollop of the reserved crabmeat mix. Enjoy!