Combine the olive oil, vinegar, parsley, cilantro, garlic, red pepper flakes, lemon juice, and cumin in a food processor and blend until smooth.
Season with salt and pepper, to taste, and set aside.
In a small glass bowl, combine the olive oil, lime juice, and chopped garlic with a fork. Season with salt and pepper, if desired.
Place the flank steak in a large, Ziploc plastic bag and add the olive oil mixture.
Tightly seal the bag and turn a couple times to coat the steak in the marinade. Place in the refrigerator for at least 1 hour to overnight.
To prepare, heat the olive oil in a large skillet over medium-high heat.
Remove the steak from the marinade and allow excess to drip off before adding to the hot skillet.
Cook the steak for 3-4 minutes, then turn and cook for an additional 3-4 minutes for medium-rare results. Adjust cooking times to reach the desired level of doneness.
Remove from heat and transfer steak to a cutting surface. Let rest for 5 minutes before cutting into very thin slices against the grain.
To serve, drizzle steak with some Chimichurri sauce and pass remaining sauce for those who prefer a little more. Enjoy!