To make Chimichurri Sauce, in a medium bowl whisk together all ingredients except oil. Allow to sit for 5 minutes.
Slowly whisk in oil until sauce is slightly emulsified. Season with additional salt, if needed.
To make Argentinian-Style Churrasco Skewers, in a shallow dish lay out strips of beef and season with salt and pepper. In a small bowl mix together olive oil, garlic, juices, paprika, and cumin; pour over beef strips. Cover and marinate in the refrigerator for about 2 hours.
Thread each beef strip lengthwise onto a skewer. If desired, add vegetables (tomato, mushrooms, onions) on the skewer as well. Allow to sit at room temperature for 30 minutes.
Preheat the grill to high. Generously oil clean grill grates with a paper towel dipped in canola oil and held with tongs.
Grill 4 to 5 minutes on each side (if using flank steak, which is leaner and can dry out more easily, check for desired doneness after 3 minutes on each side).
Remove from grill and let it rest for 5 minutes. Serve with Chimichurri Sauce.