• 1 (2 1/2 to 3 pound) tri tip steak, fat cap trimmed to 1/4-inch thick
• 1 teaspoon toasted sesame oil
• 1 tablespoon kosher salt, divided
• 2 tablespoons unsalted butter, cut into 1/2-inch cubes
• 1 tablespoon coriander seeds, coarsely ground
• 1 tablespoon black peppercorns, coarsely ground
• 2 tablespoons grapeseed oil

Chile-Lime Dipping Sauce

• ½ cup fresh lime juice (from 3 large limes)
• ½ cup fish sauce
• ¼ cup dark brown sugar
• 4 medium garlic cloves, grated with a Microplane grater (about 2 tsp.)
• 1 (1 inch) piece fresh ginger, peeled and grated with a Microplane grater (about 1 1/2 tsp.)
• 2 medium green onions, white bottoms finely chopped and green tops thinly sliced crosswise (about 2 Tbsp. minced white bottoms, about 1/4 cup thinly sliced green tops)
• 1 tablespoon toasted sesame seeds
• ½ teaspoon toasted sesame oil

1. Prepare a thermocirculator and water bath according to manufacturer’s directions. Set thermocirculator to 135 degrees F (57 degrees C) and allow water bath to come up to temperature.
2. Using gloved hands, rub tri tip steak evenly with sesame oil and season evenly with 1 teaspoon salt. Transfer tri tip and butter to a large vacuum-sealable bag and arrange in a flat, even layer. Seal bag with a vacuum sealer according to manufacturer’s directions.
3. Transfer vacuum-sealed tri tip to warm water bath with thermocirculator, cover vessel with aluminum foil to reduce evaporation, and cook 3 hours. Remove tri tip from bag (meat will be at 135 degrees F (57 degrees C) when pulled from water bath) and transfer to a rimmed sheet pan lined with paper towels and gently pat dry; discard bag and any juices reserved in bag.
4. Meanwhile prepare the chile-lime dipping sauce. Whisk together lime juice, fish sauce, brown sugar, garlic, ginger, green onions, sesame seeds, and toasted sesame oil in a small bowl until well combined. Cover dipping sauce with plastic wrap and set aside at room temperature until ready to use.
5. Season tri tip evenly with remaining 2 teaspoons salt, coriander seeds, and black peppercorns, pressing coriander and black peppercorns into tri tip to adhere.
6. Heat grapeseed oil in a large cast iron skillet over medium-high heat. Add tri tip to skillet, fat-cap-side down, and cook, until all sides are evenly seared and caramelized, 3 to 5 minutes per side.
7. Transfer tri tip to a large cutting board and let rest for 5 minutes before slicing against the grain into 1/4-inch-thick strips.
8. Serve steak with chile-lime dipping sauce for dipping, if desired.