Peel the potatoes and cut into roughly 1-inch cubes. Place in a small pot with cold water to cover and two teaspoons of the salt.
Bring to a boil, then simmer for about 10 minutes, until tender.
Drain and return to pot.
In a small bowl, stir together the sour cream, remaining ½ teaspoon salt, onion powder, paprika, cumin, garlic powder, black pepper, and cayenne.
Add mixture to potatoes and mash until smooth.
One by one, heat the tortillas on both sides in a dry 12-inch frying pan.
Spread a generous two tablespoons of potato into each tortilla and gently fold to form a taco.
When all tacos are assembled, heat the oil in the same frying pan until thin and shimmering.
Working three to four tacos at a time, fry on one side until crisp, about 90 seconds, then flip and repeat. Drain on paper towels and sprinkle with a little additional salt if you like.
To serve, add some cheese, cilantro and red onion to the top of each taco (or gently open it and place inside),