1 cup lightly-packed organic parsley leaves, roughly chopped
1 tablespoon capers
2 organic green garlic bulbs (white and light green parts only), sliced (or 5 regular garlic cloves)
Zest of 1/2 organic lemon
Juice of 1/2 organic lemon, plus more to taste
Pinch of red pepper flakes
1/4 cup extra-virgin olive oil
Add garlic, rosemary, lemon juice and olive oil to a small bowl, whisking to combine. Set aside.
Trim the fat cap off of the tri-tip roast, but be sure to leave some fat on the outside. This will help with flavor and texture. Discard trimmed fat. Transfer roast to a plate or small baking dish. Season both sides of the roast generously with kosher salt and freshly ground black pepper. Pour the marinade (garlic-rosemary mixture) over the tri-tip, and let sit for 30 minutes to 1 hour. Turn the roast over in the marinade every 15 minutes to ensure even flavoring.
Meanwhile prepare an outdoor grill. Cooking a tri-tip requires both direct and indirect heat. If using a charcoal grill, pile up your coals on one half of the grill. The side with the coals will be used for direct heat cooking, and the cooler side will be used for indirect heat. If using a gas grill, preheat one side of the grill on high, and leave the other side off (no heat). With either method, let the grill grate preheat for 15 minutes. Also, the grate should be cleaned and oiled just before cooking.
Take the tri-tip from the marinade, and let any excess liquid drip off. Place the roast over direct heat, and sear for 3 – 4 minutes per side. Move the roast over to the indirect heat side, cover, and cook until the roast reaches 120°F for rare, 130°F for medium-rare, and 140°F for medium (20 – 35 minutes). You’ll want to maintain a grill temperature of 250°F to 300°F, and be sure to flip the roast every 10 minutes. Let the tri-tip rest for 10 minutes before carving.
While the roast is resting, prepare the salsa verde. Place parsley, capers, garlic, lemon zest, lemon juice, red pepper flakes, and kosher salt (I used about 1/2 teaspoon) in a food processor, pulsing until all ingredients are chopped and well-combined. Scrape down the sides. With the motor running, slowly stream in the olive oil. Stop after you’ve added 1/ 2 the oil, scrape down the sides, and then add the rest of the oil. Transfer salsa verde to a small bowl, and season to taste with additional kosher salt and lemon juice.
Slice the tri-tip against the grain, and serve with salsa verde. Be sure not to slice with the grain as this will result in tough, chewy slices of beef.