Preheat the oven to 200°C (400°F). Place the cherry tomatoes on a rimmed baking sheet and drizzle with olive oil, salt, and black pepper. Toss directly on the tray to coat evenly, then spread in a single layer — crowding the tomatoes causes them to steam rather than roast, which produces a different and inferior result. Roast for 12–15 minutes until the skins are blistered and split and the tomatoes have collapsed slightly and taken on caramelized color at their edges. The goal is concentrated, intensely sweet tomatoes with some structural integrity remaining rather than fully collapsed sauce. The juices that pool on the baking sheet are valuable — scrape them up and include them when adding the tomatoes to the finished bowl. Set aside to cool to warm or room temperature before assembly.

Pat the sirloin steak completely dry on all surfaces with paper towels — moisture on the surface of meat creates steam when it hits the pan, which prevents the Maillard reaction browning that produces the flavourful crust this salad depends on. Season generously on both sides with the kosher salt and black pepper, pressing the seasoning firmly into the surface. Allow to rest at room temperature for 15 minutes — this is not a courtesy step but a practical one that reduces the temperature gradient between the steak's exterior and interior, producing more even cooking throughout. Heat a large cast iron skillet over high heat for 3 full minutes until smoking. Add the olive oil and swirl to coat. Lay the steak in the pan and do not move it — allow it to sear undisturbed for 3–4 minutes until a deep, dark brown crust has formed on the bottom and the steak releases from the pan naturally without sticking. Flip once and sear the second side for a further 3–4 minutes. For medium-rare, pull the steak at an internal temperature of 55°C (130°F) — the temperature will continue to rise to 57–60°C during resting. Transfer to a cutting board and rest for a minimum of 8–10 minutes. Resting is not optional — it allows the muscle fibres that contracted during high-heat cooking to relax and reabsorb the juices that were driven toward the centre, redistributing moisture evenly throughout the meat.

In a medium bowl, combine the red wine vinegar, Dijon mustard, minced garlic, honey, salt, and black pepper. Whisk together until fully incorporated. The Dijon mustard in this recipe is doing two jobs simultaneously — contributing its own complex, fermented sharpness as a flavour element, and acting as an emulsifier that allows the oil and vinegar to form a temporarily stable, cohesive dressing rather than separating immediately. Begin adding the olive oil in a very thin, steady stream while whisking continuously and vigorously. The constant motion breaks the oil into tiny droplets and distributes them throughout the aqueous vinegar-mustard base, creating the emulsification that gives the finished vinaigrette its slightly creamy, unified appearance. Add the first third of the oil most slowly — once the emulsion is established it is more stable and the remaining oil can be added more quickly. Taste and adjust: the vinaigrette should be bold, garlicky, and tangy with a clean honey sweetness softening the vinegar's edge. If it tastes flat, add more salt. If too sharp, add a small additional amount of honey.

Place the pine nuts in a dry, ungreased skillet over medium heat. Toast, stirring constantly, for 2–3 minutes until golden and fragrant. Pine nuts go from perfectly golden to burnt very quickly — remove from the pan immediately to a plate the moment they reach golden color, as the residual heat of the pan will continue cooking them. Do not walk away from pine nuts at any point during toasting.

In a large mixing bowl, combine the mixed salad greens, arugula, thinly sliced cucumber, and shaved red onion. The combination of mixed greens and arugula is deliberate — mixed greens provide mild, varied texture while arugula provides the peppery, slightly bitter edge that gives the salad the character needed to stand up to the steak's richness. Shaved red onion rather than diced provides a more elegant presentation and a less aggressive onion bite — use a mandoline or the thinnest knife setting you can manage for translucent, paper-thin rings. Crumble the feta directly into the bowl from above to allow it to distribute naturally rather than clumping. Add half the vinaigrette and toss gently but thoroughly, lifting from the bottom of the bowl to coat every leaf. The dressed greens should be lightly coated — glistening rather than wet or pooling with dressing at the bottom.

After the full 8–10 minute rest, identify the grain direction of the steak — the visible parallel lines of muscle fibre running through the meat. Slice firmly against the grain into strips approximately 5–7mm thick. Cutting against the grain shortens the individual muscle fibres in each slice, which dramatically reduces the chewing resistance and produces tender, pleasant mouthfuls rather than stringy, chewy ones regardless of the cooking quality. Divide the dressed salad among four bowls. Fan the sliced steak over the top of each portion. Add the roasted cherry tomatoes alongside the steak, including any caramelized pan juices. Scatter the crispy fried shallots and toasted pine nuts over the entire surface. Drizzle the remaining vinaigrette over the steak slices specifically — they benefit most from the additional dressing as a protein without their own sauce. Serve immediately.