CHIMICHURRI SAUCE: In a food processor fitted with a metal blade, pulse lime juice and garlic. Add parsley, cilantro, oregano, red onions, red pepper flakes, salt and pepper; pulse until roughly chopped. With the food processor running on low, drizzle in olive oil, process until just combined; set aside.
STEAK: Squeeze lime on steak. In a small bowl, whisk all the spices together and press onto both sides of the steak. Allow to rest while pan heats.
Heat a large cast iron skillet or grill pan over medium-high heat. Add the tablespoon of olive oil.
Cook steak on medium high heat for 2-4 minutes per side depending on desired level of doneness. Remove pan from heat when steak reaches desired doneness. Brush with chimichurri sauce. Allow to rest for 10-15 minutes. Slice steak against the grain.
TACOS: In a medium bowl, toss together diced tomatoes, jalapeno peppers and red onion with lime juice. Build tacos by layering about 2-3 slices of beef on a corn tortilla with a spoonful of veggie mixture and an avocado slice if desired. Finish by drizzling more chimichurri on top of the tacos. Enjoy