Preheat the grill to 400 F. Brush the flesh side of each salmon filet with olive oil; set aside.
In a small dish, combine the salt, cumin, paprika, garlic powder, onion powder, ancho chili powder, and black pepper together. Sprinkle the seasoning over the salmon and rub to cover the surface.
Grill salmon, skin side down for 10-14 minutes or until flaky and cooked through.
Meanwhile, mash the avocado along the inside walls of a small bowl until just slightly chunky. Mix in the onion, lime juice, cilantro and salt. Serve grilled salmon with ¼ of the avocado salsa. Serve immediately.