Grilled Skirt Steak with Blistered Tomatoes and Guacamole

Place steak in a shallow glass baking dish. In a small bowl, whisk together cumin, coriander, garlic, 2 tablespoons lime juice, and 2 tablespoons olive oil. Pour mixture over steak, turning to coat, and marinate 10 minutes. Make guacamole: In a medium bowl, mash together avocado, onion, cilantro, red pepper flakes, and remaining 2 tablespoons lime juice until chunky, then season with salt. In a medium bowl, mix tomatoes with remaining 1 tablespoon olive oil and season with salt and pepper. Heat a grill pan over medium-high heat. Grill tomatoes until blistered, 4 minutes, then remove tomatoes and increase heat to high. Add steak to grill and season with salt and pepper. Grill 3 minutes per side for medium-rare, then let sit 5 minutes. Thinly slice steak against the grain. Top with blistered tomatoes and cilantro, and serve with guacamole.