Place salmon, 5 cups of water, and a couple pinches salt in a large saucepan. Bring to a very slight simmer, with just a few bubbles breaking the surface, and cook for 8 minutes or until fish is cooked through. Remove fish with slotted spoon and gently break apart flesh with a fork.
In a large bowl, toss together tomatoes, avocado, pineapple, green onion, jalapeno, lime juice and salt.
Divide salmon among lettuce leaves and top with salsa.