Combine the ground cumin, salt, and black pepper in a small mixing bowl; stir until thoroughly incorporated. Rub the steak on both sides with the prepared seasoning.
Drizzle olive oil over the steak and turn to coat.
At this point, you can cover the steak and let it sit in the refrigerator for 2 hours or grill it.
Preheat your grill to medium-high heat.
Transfer the steak to the heated grill and cook it to the desired doneness, about 5 minutes per side for medium-rare, which is 130˚F internal temperature.
Transfer the cooked steak to a work surface, such as a cutting board, and let it rest for at least 5 minutes before slicing.
For the Chimichurri
Add oil, lime juice, garlic, parsley, oregano, cayenne pepper, red pepper flakes, salt, and freshly ground black pepper to a food processor; pulse until the herbs are finely chopped.
Add the diced avocado to the food processor; pulse until well combined and chunky.
Cut the steak across the grain into thin strips.
Arrange the steak slices on a platter and serve with prepared avocado chimichurri sauce.