- 6 cloves garlic, crushed
- 1/3 cup chopped lemon grass
- 3 tablespoons grated fresh ginger root
- 2 tablespoons grated onion
- 1/3 cup fish sauce
- 1/4 cup seasoned rice vinegar
- 3 tablespoons soy sauce
- 2 tablespoons ground coriander
- 1 tablespoon ground cumin
- 2 teaspoons ground turmeric
- 1/2 teaspoon cayenne pepper
- 1/3 cup packed brown sugar
- 2 tablespoons vegetable oil
- 1 (2 1/2 pound) trimmed beef tri tip roast
- Place garlic, lemon grass (bruised and chopped–see note), grated gingerroot, grated onion, fish sauce, rice vinegar, soy sauce, coriander, cumin, turmeric, cayenne pepper, brown sugar, and vegetable oil in a large mixing bowl. Whisk until ingredients are thoroughly mixed.
- Transfer tri tip roast to marinade. Poke both sides of the roast numerous times with the tines of a fork to get the marinade into the roast. Cover with plastic wrap. Refrigerate 2 to 12 hours. During the marinade time, remove the meat from the fridge occasionally to turn and poke some more with a fork.
- Transfer roast to a paper-towel-lined tray to drain briefly. Reserve marinade.
- Preheat covered grill to 325 degrees F (165 degrees C). Lightly oil the grate.
- Cook roast covered, over indirect heat, basting with marinade and turning occasionally. Cook about 35 to 45 minutes, depending on how hot your grill is. An instant-read thermometer inserted into the center should read 130 to 135 degrees F (54 degrees C). Transfer roast to a cutting board and let rest at least 20 minutes before slicing.
- Place any remaining marinade in a saucepan; bring to a boil. Simmer for 1 or 2 minutes. You can use this as a serving sauce.