Preheat the oven to 400°F.
To make the salsa verde, combine the onion, jalapeño, green chile, tomatillos, and garlic on a large baking sheet. Drizzle 5 tablespoons of the olive oil and sprinkle 1 teaspoon salt on the vegetables; toss to coat. Roast until the veggies are softened and slightly charred, 15 to 20 minutes.
Transfer to a blender or food processor and add the lime juice, cilantro, broth, and cumin. Process until smooth, adding a little water to thin it down if the consistency is too thick. Set aside.
Heat a large sauté pan over high heat. Rub the steak with the remaining 1 tablespoon olive oil and lightly season it with salt and pepper. Sear the steak until nicely browned, 5 minutes per side for medium, or to your desired doneness. Let it rest 5 minutes.
Slice the steak ¼ inch thick, against the grain and on a slight diagonal. Fan the steak slices out on a serving board and garnish with the lime wedges and cilantro, if desired. Serve the warm tortillas and sauce on the side.