Combine jalapeno, garlic, kosher salt, and 1 teaspoon black pepper in a mortar. Grind into a paste.
Pour lime juice, orange juice, and vinegar into a glass bottle or lidded container; add garlic mixture and shake well. Place steak in a shallow bowl and pour marinade over. Cover with plastic wrap and refrigerate until steak absorbs flavors, 4 to 6 hours.
Preheat grill for medium heat and lightly oil the grate.
Remove steak from the marinade and place on a cutting board. Season with salt and pepper and slice against the grain into thin strips.
Grill until slightly charred and light pink in the center, about 5 minutes per side.