1. Light a grill. Preheat the oven to 350°. Spread the pecans in a pie dish and toast in the oven for about 5 minutes. Let the pecans cool, then coarsely chop them.
2. In a food processor, combine the pecans with the cilantro, cheese, stock and vinegar and process to a puree. With the machine on, gradually add the olive oil in a thin stream. Season the pesto with salt and pepper.
3. Oil the grill grates. Season the salmon with salt and pepper and grill the fillets skin side down, over moderately high heat until nicely charred and crisp, about 4 minutes. Carefully turn the fillets and grill until just cooked through, about 3 minutes longer. Spoon the pesto onto plates. Top with the fillets, skin side up, and serve.