Chimichurri is an Argentine version of pesto. The cilantro, parsley and mint that make up this easy to make sauce play beautifully with the robust flavor of beef tenderloin. If you don't have shallots, feel free to substitute with an equal amount of yellow onions.
Preheat the grill. In a small bowl, whisk together the rub ingredients.
Roll tenderloin in paper towels to remove excess moisture. Sprinkle half the rub mixture evenly over the tenderloin. If you like it spicy, continue sprinkling until youve used all the mixture. Pat the spices into the meat gently to adhere.
Place the tenderloin on the cooking grate and sear for 2 minutes on each side over direct high heat. After all the sides are seared, move to medium-high indirect heat and finish cooking, about 40 more minutes for medium-rare or until a meat thermometer inserted in the thickest spot reads 130 degrees F. (If the tenderloin is larger, it will take longer to cook.)
Transfer meat to a platter and let rest 15 minutes. Slice thinly and serve with sauce.
Put the garlic, shallots, oil, vinegar, lemon juice, salt, pepper, and red chile flakes in a blender or food processor and process until pureed. Add the parsley, cilantro, and mint a little at a time and blend until they are incorporated. You may need to scrape down the sides of the container with a spoon to aid the pureeing. The sauce should be very green and thickthe texture of pesto. The chimichurri will keep, tightly covered, in the refrigerator for up to 3 days.