Step 1 Slice the peppers lengthwise into one-eighth-inch strips (about 1 1/2 cups). Peel and slice the potatoes into one-eighth-inch slices (you'll have about 1 1/2 cups sliced). Thinly slice the onion.
Step 2 Fill a deep 11-inch frying pan with canola oil. When it is hot add the potatoes and onions. The oil should be hot enough to cook the potatoes but not so hot that it will fry and burn them, about 220 degrees. Stir occasionally so the potatoes don't stick to the bottom. Cook for 7 to 10 minutes.
Step 3When the potatoes are soft and knife-tender, add the sliced peppers. Cook for an additional 2 to 3 minutes. Remove the potatoes, onions and peppers with a slotted spoon to a paper towel-lined bowl. The oil will drain to the bottom. Let the cooking oil cool and discard.
Step 4Whisk the eggs in a separate bowl. Add the potato-pepper mixture, and gently fold to combine. Season with 2 teaspoons of salt.
Step 5In a 10-inch nonstick frying pan, add two tablespoons olive oil. Heat over medium heat. When it is hot, swirl it around so that it coats the pan. Pour in the egg-potato mixture and gently move the pan in a circular motion a few times so that the egg doesn't stick. Smooth out the potatoes on top, if necessary, to make an even surface. Cook on medium heat for 5 minutes and then reduce the heat to low. Cook until the tortilla starts to bubble, and the sides are firm and somewhat set, about 20 minutes.
Step 6To turn the tortilla, place a large flat plate over the frying pan and turn the tortilla onto the plate. If the frying pan is dry, add additional oil as needed. Gently slide the uncooked side of the tortilla back into the pan. Cook 1 to 2 minutes, until golden and set, again moving the pan in circular motions. Remove from the heat, place a large serving plate over the pan and carefully invert on to the plate. Sprinkle with the chopped parsley and serve.