Since the mayonnaise contains raw eggs, use it the day it is made.
Place the beets in a large saucepan, and fill with enough cold water to cover by 2 inches. Add salt, and bring to a boil. Reduce heat, and simmer until the beets are tender when pierced with a fork, about 20 minutes. Drain, and let stand until cool enough to handle. Carefully rub off the beet skins using a paper towel, and set cooked beets aside.
Prepare an ice bath, and set aside. Fill saucepan halfway with water, and bring to a boil. Add salt and the asparagus, and cook until the asparagus is bright green and tender enough to bend without breaking, about 4 minutes. Using a slotted spoon or tongs, carefully transfer the asparagus to the ice bath to stop cooking. Drain immediately, and pat asparagus dry. Set aside.
In a blender, combine the egg yolk, mustard, and lemon juice. With blender running, add the olive oil and then canola oil in a slow, steady stream until mixture emulsifies and forms a thick mayonnaise. Season with salt and pepper. Transfer to an airtight container, and refrigerate for at least 1 hour. Mayonnaise will thicken when refrigerated. Serve chilled with the beets and asparagus, for dipping.
Raw eggs should not be used infood prepared for pregnant women,babies, young children, the elderly, oranyone whose health is compromised.