Preheat the oven to 200C, fan-forced. Line an oven tray with baking paper. Crush or finely chop the garlic, then using the flat side of the knife, mash to a paste (see cooking tip). Combine the South American seasoning, half the garlic and 2 tsp olive oil in a large bowl and season with salt and pepper. Add the beef and turn to coat.
Step 2 — Cook beef
Heat a medium frypan over high heat until hot. Cook the beef, turning regularly, for 2 mins or until browned. Transfer to the lined tray. Roast the beef for 14-16 mins for medium-rare, or until cooked to your liking. Remove from the oven and rest for 10 mins.
Step 3 — Prep ingredients
Meanwhile, cut the tomato into thin wedges. Thinly slice the radish. Finely chop the parsley, including the stems. Thinly slice the spring onion.
Step 4 — Make salad
Put 1½ tbs extra virgin olive oil, 3 tsp red wine vinegar and ¼ tsp sugar in a bowl and stir until the sugar dissolves. Transfer 2 tsp of the dressing to a large bowl. Add the salad leaves, tomato and radish to the dressing in the large bowl and toss to coat.
Step 5 — Make chimichurri sauce
Stir the parsley, spring onion and remaining garlic into the remaining dressing and season with salt and pepper.
Step 6 — Heat tortillas and serve
Heat a large frypan over medium-high heat. Warm the tortillas, one at a time, for 30 secs each side or until warmed through and slightly charred. Cover with a clean tea towel to keep warm. Slice the beef. Divide the tortillas among plates, then fill with the beef and salad. Drizzle with the chimichurri sauce to serve.