Combine the marinade ingredients in a food processor and process for approx. 10-20 seconds until the cilantro stems and jalapeno are chopped into very small pieces.
Within 2 hours before grilling, place your salmon in a non-reactive container and pour over the marinade to coat the fish.
Prepare your grill to a high temperature. Brush the grate with an vegetable oiled paper towel. Place the salmon skin side down on the grate. Close the lid and lower the temperature to "Low". Cooking time will depend on the thickness of the fish.
The salmon is cooked when, if you take a knife and slice through the thickest part, the flesh is opaque and firm. Take care not to overcook the fish. Remember that it will continue to cook a few minutes after you remove it from the grill.
Near the end of the cooking time, brush the fish with some of the marinade and allow it to cook.
Remove the fish from the grill. Let it rest a few minutes. Serve.