Toss the onions with 2 tablespoons each vinegar and cold water and a large pinch of salt in a small bowl. Let sit for at least 30 minutes, tossing occasionally. (The onions will turn bright pink.) Strain.
Meanwhile, set up a steamer in a pot of simmering water. Add the asparagus, and steam until bright green and crisp-tender, 6 to 8 minutes. Remove, spread out on a baking sheet and let cool.
Whisk together the buttermilk, Parmesan, mayonnaise, garlic, the remaining 1 tablespoon vinegar, 1/2 teaspoon salt and a few grinds of pepper in a small bowl.
Using a straight-sided 3-quart tall glass bowl for 1 large salad or four 16-ounce wide-mouth glass jars with lids for 4 individual salads, make a first layer with half the arugula, then add the following in separate layers: the radishes, half the broccoli, the snap peas, the pickled red onion, the remaining arugula, the remaining broccoli, and the asparagus and egg. Sprinkle the top with the almonds. (The salad can be put together, covered and refrigerated for up to 2 hours before serving.)
If making 1 salad, just before serving, transfer it to a large bowl, toss with about half the dressing and season with salt and pepper. If making 4 salads, add dressing to each jar, season with salt and pepper, cover with the lid and shake to coat. Serve the remaining dressing on the side.
To achieve pretty, defined layers, be sure to layer more on the sides. It's OK if there isn't enough of an ingredient to fill the middle.From Food Network Kitchen