Wash the potatoes thoroughly and cook them covered in 2 l boiling salted water for about 20 minutes. Drain potatoes, quench, peel and let them cool down. Clean, wash and cut the peppers into strips.
Sort the spinach, place in a sieve, rinse cold, drain and chop coarsely. Peel onion and garlic and chop finely. Cut potatoes into approx. 0.5 cm thick slices. Crumble feta coarsely.
Heat 4 tablespoons of oil in an ovenproof pan (28 cm Ø) with lid. Fry the potatoes for about 12 minutes, turning them over. Season with salt, pepper and 1 pinch of cayenne pepper. After about 8 minutes add paprika, onion and garlic.
Fold the spinach and feta into the potatoes.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Whisk eggs, milk, approx. 1⁄2 tsp. salt and pepper. Pour the egg milk over the potato and vegetable mixture, cover and allow to set at low heat for approx. 10 minutes.
Finish cooking in a hot oven for 10-15 minutes.
Wash parsley, shake dry, pluck off leaves and chop finely. Roughly chop the capers. Mix parsley, capers and 4 tablespoons of oil. Season with salt and pepper. Take the finished tortilla out of the oven and let it rest in the pan for about 5 minutes.
Then turn out of the pan onto a plate. Spread parsley-capers mixture on it. Tastes almost a little better the next day - cold or warm.