Place 1 cup of the water into the Instant Pot. Top with a steamer basket. Arrange the eggs in the steamer basket. Seal the lid, close the valve, and set the Manual/Pressure Cook button to 7 minutes.
Meanwhile, combine the remaining 2 cups of water with the ice cubes in a medium bowl and place near the Instant Pot.
In a small bowl, stir together the mashed avocado, jalapeño, mayonnaise, lemon juice, mustard, and salt.
Use a quick pressure release. When the valve drops, carefully remove the lid and place the eggs immediately into the ice water. Let stand for 3 minutes.
Peel the eggs and cut the eggs in half, discarding 4 of the egg yolk halves. Add the remaining egg yolk halves to the avocado mixture and mash until well blended (it will be slightly lumpy). Finely chop all of the egg whites and set aside.
Spread the avocado mixture on bread slices (dividing it evenly between the slices) and top with the chopped egg whites, tomato, cilantro, and onion. Serve with the lemon wedges to squeeze over all.