Cut the potatoes
Peel the cooked potatoes and cut them onto 2 x 2 cm (0.8 x 0.8 inch) cubes. Peel and thinly slice the onions.
Add the ingredients into skillet
Heat the olive oil in a nonstick skillet (approx. 23 cm / 9 inch). Add the onions and cook over low heat until the onions are nice and soft, about 10 minutes, stirring regularly. Add the potatoes and Delamaris Tuna Provencale, season to taste with salt and pepper, and cook for another 5 minutes.
In a bowl beat together the eggs and sour cream. Pour the mixtures over the potatoes and shake your skillet, arranging potatoes to submerge. Cover with a lid and cook for about 20 - 25 minutes over low heat, regularly shake your skillet so that the tortilla doesn't get burnt on the bottom. If the eggs on top won't be completely cooked after 25 minutes, invert your tortilla onto a large plate. Slide back into skillet browned side up. Cook until golden on bottom and cooked through, for about 5 more minutes.
Serve your Potato Tortilla with Tuna Provencale warm or at room temperature. Cut into wedges and serve with seasonal salad or a dollop of sour cream. Store any leftovers in a fridge for up to 2 days - reheat in the oven. Enjoy.