Make the salad: Place the red onion in a small bowl and cover with water. Let it rest while you prepare the rest of the salad. Place the arugula in a large serving bowl.

To toast the almonds, place them in a small skillet over medium-low heat. Cook, stirring frequently, until the almonds are fragrant and starting to turn golden on the edges, about 4 to 5 minutes. Set aside.

Make the dressing: In a small bowl or large liquid measuring cup, whisk together the dressing ingredients (the oil, lemon juice, mustard, garlic, salt, and pepper).

Drizzle half of the dressing over the greens, then toss to coat. Drain the red onion, then scatter it over the arugula. Top with the peaches, avocados, almonds and cheese. Just before serving, drizzle on a bit more dressing and give it a final, gentle toss to combine. Enjoy, with additional dressing as desired.