Mix together the sour cream, yogurt, cumin, curry powder, garlic and jalapeno.

Lay the steak in a glass, ceramic or nonreactive dish. Pour the marinade over the steak and turn a few times to coat well. Cover with plastic wrap and refrigerate for 6 to 8 hours or overnight, turning twice.

Spray the grilling grate of a gas or charcoal grill with vegetable oil spray. Preheat the grill to medium hot.

Lift the steak from the marinade and wipe the excess from the meat. Grill the meat for 4 to 5 minutes on each side for medium rare or done to your liking.

Let the meat rest for about 10 minutes before slicing across the grain and serving.