Prepare the Chimichurri Sauce: In a medium mixing bowl, combine chopped cilantro, parsley, minced garlic, red chili, red wine vinegar, dried oregano, and cumin. Mix well until all ingredients are combined, and set aside to marinate for at least 15-20 minutes.
Season the Steak: While the chimichurri is marinating, season the flank steak generously with salt and black pepper on both sides.
Cook the Steak: Heat olive oil in a large skillet over medium-high heat. Once hot, add the seasoned flank steak and cook for about 4-5 minutes on each side for medium rare, or cook to your desired level of doneness. Remove the steak from the skillet and let it rest for 5 minutes.
Slice the Steak: After resting, thinly slice the steak against the grain into strips.
Warm the Tortillas: In the same skillet or another pan, lightly warm the corn tortillas for about 30 seconds on each side until soft and pliable.
Assemble the Tacos: On each warmed tortilla, place a few slices of steak. Top with diced tomatoes, a few slices of avocado, and generously drizzle with the prepared chimichurri sauce.
Serve: Serve the tacos immediately with lime wedges on the side for squeezing over the tacos.
Notes
Serve the tacos on a colorful platter, garnished with extra lime wedges and a small bowl of chimichurri for dipping.