In a large bowl, add 1 cup cold water, sprinkle the gelatin on top and allow to dissolve. In the meantime, add the hot water and sugar to another bowl and stir together. Then add the white vinegar and stir until it dissolves. Pour the sugar mixture over the gelatin. Place in the freezer and stir occasionally until it thickens, about 30 minutes.
Remove from the freezer and add the asparagus, celery, pecans, pimentos, onions, lemon juice and salt to taste. Pour into a mold and place in the refrigerator until ready to serve.
Serve with mayo and lemons.