*Lemon confit: use rinds only, rinse and pat dry before mincing. It can be subbed for 2 lemon zest. Combine all ingredients together except for the vinegar (add it before serving to keep its vibrant color). Season with salt, ground black pepper and red pepper flakes or minced jalapeño to taste.
Wash potatoes and remove dark spots. Cut them into bite size portions, and soak them in cool water preventing oxidation. Drain and pat dry potatoes and mix with the sliced onions and crushed garlic (skin-on) – Rub in olive oil and spices, and season with salt and pepper. Preheat oven to 425ºF/220ºC. Bake potatoes for about 40/45 min; tossing mixture half way through. Peel off roasted garlic. Keep warm.
Leave meat out to come to room temp before grilling. Rub meat with olive oil and season with salt. Set oven to 500ºF/260ºC. Meanwhile heat up cast iron grill. Grill mark meat on both sides for 1 min. Arrange steak on a baking tray lined with silicone mat. Pop in the oven for 4 min. Transfer meat onto a tray and tent with foil loosely or use an upside down tray for 8 min.
Slice steak across the grain (perpendicular to its muscle fibers) and place next to the roasted potatoes. Cover meat with the chimichurri sauce. Enjoy!