Turn broiler on high. Blacken the poblano and bell peppers to char skins evenly all over. Place in a bowl, cover and cool. Peel, seed and stem the peppers, and place in food processor.
Line a rimmed baking sheet with foil and spray the tomatillos, onion and garlic with cooking oil. Season with salt and pepper, and char under the broiler until onions soften a bit and tomatillos blacken and burst, about 10-12 minutes. Place veggies in the food processor with the peppers along with the nuts, cilantro, parsley, mint and vinegar. Add salt and pepper, and pulse-chop into a fine mixture while streaming in EVOO. Remove to a container or bowl and reserve.
For the steak, heat a large, cast-iron skillet over medium-high to high heat. Cut steak into portions to fit in pan. (Meat can be cooked in 2 batches depending on pan size.) Season meat with salt, pepper, cumin, coriander and granulated garlic. Heat oil, 1 turn of the skillet. When pan smokes, add beef and cook until crispy and brown on both sides.
Serve steak sliced topped with Romesco sauce and a simple salad of baby kale tossed with shaved Manchego, lemon juice, EVOO and salt alongside. Add cracked or chopped olives and pimiento if you like.
*The Romesco sauce keeps up to 3 weeks in fridge and is great on any protein or charred bread or sandwich.