Place sliced meat into a shallow bowl, and season with salt, black pepper, and crushed red pepper. Squeeze the lime juice over the meat, and turn until evenly coated. Cover, and refrigerate for 30 minutes.
In a blender or food processor, combine tomatillo and jalapeno. Puree for 15 to 20 seconds, or until thick. Heat 1 tablespoon oil in a large skillet over medium high heat. Carefully pour in tomatillo mixture. Cook, stirring frequently, for 5 minutes. Stir in beef broth. Reduce heat, and simmer for 20 to 30 minutes, or until mixture coats a spoon. Transfer mixture to a serving dish.
Heat tablespoon oil in a large skillet over high heat. Stir in 1/3 of the beef, and saute for 1 minute. Transfer to serving dish. Repeat with remaining beef. Meanwhile, heat tortillas in the oven or microwave, according to package instructions.
To serve, place two tortillas on top of each other. Add desired amount of meat, spoon over some tomatillo mixture. Top with onions, tomatoes, avocado and cilantro. Garnish with a wedge of lemon, to be squeezed over taco before eating.