Make the spice mix by whisking together paprika, cayenne, dried thyme, cumin, onion powder, garlic powder, black pepper, and kosher salt in a small bowl.
Spread the spice mix onto a plate or flat surface and press each salmon fillet, flesh side down, into the spices to coat evenly on the flesh side only.
Heat a large heavy-bottomed or cast-iron skillet over medium heat and add the oil.
Place the salmon fillets flesh side down in the hot skillet and cook 2 to 3 minutes per side, or until the flesh is blackened and the skin is crispy.
Transfer the salmon to a plate to cool slightly, then remove and discard the skin with a fork or knife and shred the salmon into large chunks.
Char the tortillas directly over a gas flame or in a hot grill pan until edges are lightly browned and pliable; keep warm.
Assemble the tacos by placing shredded lettuce on each tortilla, then tomato, red onion, a portion of shredded salmon (about half a fillet per tortilla), a sprinkle of cilantro, a drizzle of salsa or sour cream, and a squeeze of lime.