In a small bowl, stir together pineapple juice, soy sauce, garlic, and cayenne pepper.

Place salmon fillets in a shallow dish and pour marinade over the fish. Cover tightly and refrigerate for 2 hours or overnight.

While the salmon marinates, prepare the salsa by combining pineapple tidbits, avocado, jalapeño, red onion, cilantro, and salt in a bowl. Drizzle with lime juice and gently toss. Refrigerate until ready to serve.

Preheat oven to 400°F. Line a baking sheet with foil and coat with nonstick spray.

Remove salmon from marinade, shaking off excess, and place fillets skin-side down on the baking sheet.

Transfer marinade to a saucepan and simmer over medium-high heat until reduced by half, about 6 minutes.

Brush glaze generously over salmon and bake for 5 minutes. Brush again and bake an additional 5–10 minutes until salmon flakes easily.

Serve immediately topped with pineapple avocado salsa.