Measure and divide the oil: reserve 2 teaspoons of the extra virgin olive oil for cooking and use the remaining 1/2 cup for the sauce.
In a blender or food processor, combine 1 cup roughly chopped cilantro, 2 cloves garlic (roughly chopped), 1/2 cup extra virgin olive oil, 3 tablespoons lemon juice, 1/2 teaspoon ground cumin, 1/2 teaspoon ground chili powder and salt and pepper to taste. Purée until smooth, stopping to scrape down the sides if needed.
Taste the sauce and adjust salt and pepper as desired. Transfer the sauce to a bowl and set aside.
Pat the 2 (10– to 12-ounce) flat iron steaks dry with paper towels. Sprinkle both sides of each steak with salt and pepper.
Heat a large skillet over medium-high heat until hot. Add the reserved 2 teaspoons extra virgin olive oil and swirl to coat the pan.
Add the steaks to the skillet without crowding. Cook to desired doneness: about 3 minutes per side for medium-rare or 4 to 5 minutes per side for medium. Flip steaks once using tongs.
Transfer the steaks to a cutting board, tent loosely with foil, and let rest for 5 minutes.
Thinly slice the steaks against the grain and serve with the spicy cilantro sauce on the side or spooned over the slices.