PINEAPPLE SALSA: In a large bowl, toss together pineapple, cilantro, red onion, Serrano pepper (Use gloves when handling the Serrano pepper), lime zest, lime juice, and salt. Cover and chill until ready to use. Make at least 30 minutes ahead of time to allow the flavors to marry.
CILANTRO LIME COLESLAW: In a small bowl, whisk together mayonnaise, lime juice, rice vinegar, garlic, Sriracha, and sugar until the sugar is dissolved.
In a large bowl, toss together coleslaw, red onion and cilantro. Pour dressing over the slaw; toss to coat. Cover tightly and chill until ready to serve tacos.
BLACKEN SEASONING: In a small bowl or ramekin, stir spices together. Sprinkle blacken seasoning liberally over salmon fillets.
SALMON: Indoors (with the overhead fan on) OR outdoors on a gas or charcoal barbecue grill, heat a cast iron skillet over medium-high heat, until it is very hot (smoking).
Place a pat of coconut oil in the hot skillet. Sear seasoned salmon, flesh side down for 2 minutes. With a spatula, flip the fish over, adding another pat of coconut oil to the pan, cook for about 2 minutes more.
ASSEMBLE TACOS: Warm corn tortillas, top with cilantro-lime coleslaw, blackened salmon, pineapple salsa, and crumbled cotija cheese. Serve with lime wedges.