Spring Layered Salad with Asparagus and Buttermilk Dressing

Name: Spring Layered Salad with Asparagus and Buttermilk Dressing
Ingredients: 1/2 small red onion, thinly sliced; 3 tablespoons white wine vinegar; Kosher salt; 1 bunch asparagus, trimmed and cut into 1-inch pieces; 1/2 cup buttermilk; 1/2 cup grated Parmesan (about 2 ounces); 3 tablespoons mayonnaise; 1 small clove garlic, finely grated; Freshly ground black pepper; 8 cups baby arugula (about 5 ounces); 6 radishes, quartered; 1 cup broccoli or alfalfa sprouts; 2 cups freeze-dried snap peas or green beans; 4 hard-boiled eggs, cut into wedges; 1/2 cup roasted almonds, chopped