Prepare the Vinaigrette Base Finely mince the tender white core of the lemongrass stalks. Grate the ginger and mince the garlic. In the small jar, combine the minced lemongrass, grated ginger, garlic, avocado oil, sesame oil, tamari, monk fruit sweetener, and sambal oelek. Zest one of the limes directly into the jar. Secure the lid and shake vigorously until the sweetener dissolves.

Season the Steak Pat the flank steak dry with paper towels. Pour about one-third of the vinaigrette over the steak, using your hands to coat all sides. Season generously with salt and pepper. Let it rest on the counter while you prepare the salad components.

Assemble the Salad Foundation Thinly slice the red bell pepper and red onion. Halve the cucumber lengthwise and cut it into thin half-moons. In the large salad bowl, combine the mixed greens, sliced bell pepper, onion, cucumber, and the whole mint and cilantro leaves.

Sear the Flank Steak Place the cast-iron grill pan over high heat. Once very hot, lay the steak on the pan. Cook for 3–5 minutes on each side for a medium-rare finish (125−130∘F or 52−54∘C). The steak should have distinct grill marks and release easily from the pan. For medium, cook for 5–6 minutes per side.

Rest and Slice the Beef Transfer the seared steak to the cutting board and let it rest for a full 10 minutes. This is crucial for retaining juices. While it rests, proceed to the next step.

Finalize the Vinaigrette Juice both limes (you should have about ¼ cup or 60 ml) and add the juice to the remaining vinaigrette in the jar. Shake again to combine everything into a bright, cohesive dressing.

Toss and Plate Thinly slice the rested steak against the grain. Pour about two-thirds of the finalized vinaigrette over the greens in the bowl and toss well to coat. Divide the dressed salad among four plates. Arrange the steak slices over the top, drizzle with any remaining vinaigrette, and finish with a sprinkle of chopped toasted cashews.