Preparation

• Heat a grill pan over medium-high heat, or prepare a medium-high (400°F to 475°F) gas or charcoal-grill fire.
• Combine the 1 tsp. oil and the soy sauce in a small dish; rub over the steak. Season the steak with salt and pepper. Grill, flipping once, until medium rare (130°F to 135°F), about 5 minutes total. Transfer to a cutting board.
• In a large bowl, whisk the vinegar, maple syrup, mustard, garlic, 1/2 tsp. salt, and a few grinds of pepper. Slowly whisk in the remaining 1/4 cup oil. Add the plums, and toss well. Using a slotted spoon, transfer the plums to a small bowl. Add the greens and onion to the dressing, and toss well. arrange on a serving platter. Slice the steak thinly across the grain. Arrange the steak and plums over the greens, and top with the cheese.