For the roasted red pepper relish: Preheat a grill over high heat. Combine the peppers with 1 tablespoon of the oil in a metal bowl and sprinkle with salt. Grill until the skins are well charred and blistered, about 10 minutes, turning once. Return the peppers to the bowl, cover with plastic wrap and allow to cool completely, about 30 minutes.
Peel the peppers and remove the seeds. Cut into thin strips. In a second bowl, combine the peppers with the vinegar, remaining oil and salt to taste.
For the tortilla Espinola: Heat the oil in a medium skillet over medium heat. Add the potatoes onions, sprinkle with salt and pepper and cook, stirring often, until the potatoes are cooked through and the onions are soft, about 8 minutes.
Crack the eggs into a large bowl, sprinkle with salt and pepper and whisk until thoroughly mixed. Using a slotted spoon, scoop the potato/onion mixture into the eggs, making sure to keep the oil in the skillet, and stir to combine.
Heat an 8-inch nonstick pan over medium heat. Add 2 tablespoons of the reserved oil from cooking the potatoes and onions. Pour the egg/potato/onion mixture into the pan and cook until the sides of the eggs have set and the middle is beginning to set, 3 to 4 minutes. Place a plate on top of the pan and invert, then gently slide the tortilla back into the pan, browned-side up. Cook for 3 minutes more, and then remove from the heat.
Serve the tortilla Espinola with the roasted red pepper relish.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.