Toast the cumin seeds in a medium saute pan over medium-low heat for 5 minutes, or until fragrant.

In a blender, combine the cumin seeds, jalapenos, garlic, pepper, lime juice, and salt. Pulse the blender to finely chop ingredients. Add the oil and cilantro and puree until smooth.

Lightly score both sides of the meat with a knife so that the marinade will penetrate. Place the meat in a large plastic bag or bowl, pour in the marinade, and coat well. Marinate in the refrigerator for 24 to 48 hours.

Preheat an outdoor grill for high heat and lightly oil grate.

Remove the meat from the marinade and discard the remaining marinade. Cook on high, 1 to 2 minutes per side, to sear the meat. Turn the heat down to low and cook for an additional 3 to 4 minutes per side, or until the it has reached the desired doneness.