Nopalito Salad (Prickly Pear Cactus Salad)

Dressing:
1/2 teaspoon salt, or to taste
1/4 teaspoon pepper
1/2 teaspoon dry mustard
1/4 cup vinegar
1/2 cup oil
1/4 teaspoon Mexican oregano
1/2 cup sour cream

Salad:
1 small yellow onion, halved and cut into strips
1 1/2 cup canned nopal cactus, chopped
1 (3 ounce) jar pimentos, rinsed, or 2 bell peppers, diced
2 cups jicama, chopped

Whisk or blend dressing ingredients vigorously to combine. Adjust seasonings to taste. Place the onions in a colander. Pour about 1 quart boiling water over them. This removes the raw taste and leaves the onions crisp. Rinse immediately with cold water and let stand. Toss together the onions, cactus, pimentos or red bell peppers and jicama. Toss the dressing and salad together just prior to serving.