Roman pizza con patate. Adapted from smitten kitchen
Soak thinly sliced potatoes in warm salted water for 1-12 hours. Preheat oven at 500 deg F (~250 deg C). Oil baking pans (I used a pizza stone). Drain and dry potatoes. Toss them with onions and pepper (any other toppings you like as well). Sprinkle with rosemary. Bake 25-30 minutes. Serve.
P.S. Similar ingredients to my attempt at Tortilla Espanola / tortilla de patatas, but with a base made of eggs instead of pizza dough. This was way too much potatoes for my dough, so I used the excess and just baked them like a gratin or roast. Also I wanted to get rid of some mozzarella and grana padano.