Preheat the oven to 220C, fan-forced. Line 2 oven trays with baking paper. Combine the barbecue seasoning and 2 tsp olive oil in a large bowl and season with salt and pepper. Add the beef and turn to coat. Cut the unpeeled sweet potatoes into thin wedges. Halve the carrot widthwise, then cut into 1cm-thick wedges.
Step 2 — Roast wedges
Put the sweet potato and carrot on a lined tray. Drizzle with 2 tsp olive oil, season with salt and pepper and toss to coat. Roast on the upper oven shelf for 25 mins or until golden and tender.
Step 3 — Roast beef
Meanwhile, heat a medium frypan over high heat until hot. Cook the beef, turning regularly, for 2 mins or until browned. Transfer to the remaining lined tray. Roast the beef on the lower shelf for 12-14 mins for medium-rare, or until cooked to your liking. Remove from the oven and rest for 10 mins.
Step 4 — Prep aji verde sauce
While the beef is roasting, crush or finely chop the garlic. Reserve a few coriander leaves, then coarsely chop the remaining coriander, including the stems. Coarsely chop the jalapeno, removing the seeds if less heat is desired (the chilli is optional; omit it if you prefer).
Step 5 — Make aji verde sauce
Put the garlic, chopped coriander, jalapeno, 1 tbs extra olive oil and 2 tsp white wine vinegar in a jug. Blend with a stick blender until smooth. (If you don't have a blender, finely chop the coriander and jalapeno; combine with the garlic, oil and vinegar in a bowl.) Stir in the aioli. Taste, then season with salt and pepper.
Step 6 — Get ready to serve
Thinly slice the beef. Divide the beef and sweet potato and carrot wedges among plates. Scatter over the reserved coriander leaves and serve with the aji verde sauce.