Sliced steak and bold blue cheese over greens — this is the salad for people who think salads are boring. Low carb lunch with steakhouse energy.
Pat the sirloin steak dry with paper towels, then season generously with salt and black pepper on both sides.
Heat 1 tbsp olive oil in a heavy skillet over medium-high heat until shimmering; sear steak for 3–4 minutes per side (for medium-rare), then let rest on a cutting board for 5 minutes.
While the steak rests, whisk together the remaining olive oil, red wine vinegar, Dijon mustard, and a pinch of salt and pepper to make the dressing.
In a large bowl, toss together mixed salad greens, cherry tomatoes, cucumber, and red onion with half of the dressing; arrange on serving plates.
Slice the rested steak thinly against the grain; lay atop salads. Add avocado slices and crumbled blue cheese, then drizzle with remaining dressing before serving.