1. Preheat grill to high.
2. Mash avocados in a medium bowl with a fork. Stir in cilantro, 2 tablespoons lime juice, 3/4 teaspoon salt and 1/4 teaspoon pepper.
3. Brush scallions and poblanos with 2 teaspoons oil. Combine ancho chile, cumin, 1/2 teaspoon salt and the remaining 1/4 teaspoon pepper in a small bowl. Rub both sides of steak with the remaining 1 teaspoon oil and the spice mixture.
4. Oil the grill rack (see Tip). Grill the poblanos, turning often, until wilted and charred, 8 to 12 minutes. Transfer to a medium bowl and cover with a plate to trap the heat. Grill the scallions, turning frequently, until softened and lightly charred, 2 to 4 minutes. Grill the steak 2 to 3 minutes per side for medium-rare. Transfer the steak to a cutting board, tent with foil and let rest.
5. Meanwhile, slice the scallions into 1-inch pieces and transfer to a serving dish. Peel as much skin as possible from the peppers, discard the stems and seeds, and slice into 1/2-inch-wide strips; transfer to the serving dish. Add the remaining 1 tablespoon lime juice and 1/4 teaspoon salt to the vegetables and toss to combine. Slice the steak very thinly, then chop into small pieces. Serve the steak and vegetables with the mashed avocado, lime wedges, hot sauce and tortillas.

Yield: 6 servings