Remove the picanha from the fridge 30 minutes before cooking.
Using a sharp knife, lightly score the fat cap in a criss-cross pattern, taking care not to cut into the meat.
Rub the picanha with olive oil, sea salt and cracked black pepper.
Preheat a BBQ or oven to medium-high heat.
Place the picanha fat-side down first and cook for 8-10 minutes until the fat is golden and rendered. Turn and continue cooking until the internal temperature reaches approximately 52°C for medium rare, around 25-35 minutes depending on thickness.
Remove from the heat, cover loosely with foil and rest for at least 15 minutes.
While the meat rests, combine all chimichurri ingredients in a bowl and mix well. Set aside.
Cook the corn on the BBQ until lightly charred on all sides. Allow to cool slightly before slicing the kernels from the cob.
Combine the corn kernels, cherry tomatoes, red onion and avocado in a large bowl. Add lime juice, olive oil, salt and pepper, then toss gently.
Slice the rested picanha across the grain into thick slices.
Serve topped with chimichurri alongside the charred corn salad.