Make the peperonata
In a 12-inch skillet, heat 1 Tbs. of the oil over high heat until it shimmers. Add the onion, 1/2 tsp. salt, 1/2 tsp. pepper, and 1-1/2 tsp. of the cumin. Cook until the onion begins to soften, about 2 minutes. Transfer to a large bowl. Add 1 Tbs. of oil to the skillet. When it begins to shimmer, add the peppers, 1/2 tsp. salt, 1/2 tsp. pepper, and the remaining 1/2 tsp. cumin and cook until the peppers are soft and charred in spots. Transfer to the bowl with the onion and let cool.
Toss onions and peppers with the vinegar, remaining 1 Tbs. of oil, and the cilantro. Adjust the seasoning as needed with salt, pepper, and cumin. Set aside.
Make the mole
Heat the oven to high broil with a rack positioned 3 to 4 inches from the top.
Arrange the tomatillos on a foil-lined rimmed baking sheet. Drizzle with 1 Tbs. of the oil and season with 1/2 tsp. salt and 1/2 tsp. pepper and toss until coated. Broil, turning occasionally, until completely blackened, about 8 minutes. Remove from the oven and set aside. When the tomatillos are cool, transfer to a blender with any accumulated juices and set aside.
In a 12-inch skillet, heat 3 Tbs. of the oil until it begins to shimmer. Add the onion, garlic, 1/2 tsp. salt, and 1/4 tsp. pepper and cook until fragrant and soft, about 5 minutes. Using a slotted spoon, transfer the onion to the blender with the tomatillos, leaving the oil behind. Add the walnuts and seeds to the skillet and toast until just beginning to brown, about 1 minute. Add the tortilla chips and stir until incorporated. Transfer the mixture to the blender with a slotted spoon and let cool, about 5 minutes. Add the broth, cilantro, and lime juice to the blender and purée until smooth. Add additional chicken broth if necessary, until the mixture has the consistency of a medium-thick sauce. Adjust the seasoning to taste with additional lime juice, salt, and pepper.
Heat the remaining 2 Tbs. oil in a clean 12-inch skillet over medium-high heat until it begins to shimmer. Transfer the mixture in the blender to the skillet, lower the heat to medium, and fry, stirring frequently, until the mixture turns light golden brown, about 4 minutes.
Cook the steak
Position a rack in the center of the oven and heat the oven to 475°F.
Dry the steak on all sides with paper towels. Generously season with 1 tsp. salt, 1/2 tsp. pepper, and the cumin. Heat a 12-inch cast-iron skillet on high for 2 minutes. Add the oil to the skillet. When it begins to shimmer, add the steak and sear on all sides until it’s golden brown and caramelized. Transfer the steak in the skillet to the oven and roast for 4 minutes. Flip the steak and roast for another 4 minutes, or until an instant-read thermometer registers 125°F for medium rare.
Remove the steak from the skillet to a rack and tent lightly with foil for 15 minutes.
Thinly slice the steak. Fill the tortillas with steak, peperonata, mole, scallions, and jalapeños and serve right away.
Photo: Jody Horton
Recipe adapted from Moveable Feast with Fine Cooking.