Knead the flour, butter, egg, mineral water and salt into a shortcrust pastry and place in the refrigerator for 1/2 hour.
Core and finely dice the peppers, peel and dice the onions. Sweat the vegetables in a pan with the lid closed until they are translucent and have lost some of their volume, this takes about 15-20 minutes. Remove the vegetables from the heat and let them cool down.
Roll out the dough and line a greased springform pan with it, prick the bottom several times with a fork.
Mix the vegetables, eggs, cheese, ajvar, tomato paste and crème fraîche together and season with salt and pepper. Distribute the mixture evenly in the springform pan.
Bake at 200 ° for approx. 35 - 45 minutes. Serve warm.