Lightly oil the grill grates (or brush salmon skin with oil to prevent sticking).
Place salmon skin-side down on the hot grill. Grill for 3–4 minutes, then gently flip with a spatula. Cook the second side for 2–4 more minutes, or until salmon is just cooked through and flaky.
Remove from grill and let rest for 2–3 minutes.
In a mixing bowl, gently combine pineapple, avocado, red bell pepper, red onion, lime juice & zest, cilantro, scallions, salt to taste and add jalapeño if desired. Toss gently to combine. Chill in the fridge until ready to serve.
Place grilled salmon fillets on each plate. Top with a generous spoonful of pineapple-avocado salsa.
Serve with grilled corn (optional), Steamed rice or a fresh summer salad.