Put the flour and salt into a bowl, make a well in the middle and pour in the cold water. Add the butter in cubes and knead everything into a dough. Wrap the dough in cling film and leave to rest in the fridge for a good hour.
Dice the onions, sauté them in a pan with butter, add the wild garlic at the end and remove the pan from the heat.
Mix the eggs, sour cream and goats cheese together, season with salt, nutmeg and pepper. Pour this mixture into the pan and fold into the wild garlic and onion mixture.
Roll out the dough on a floured surface, then position it in the tart tin and press down lightly. Pour the goats cheese and wild garlic mixture onto the pastry and spread evenly. A little grated cheese can be sprinkled over the top if you so wish.
Bake in a preheated oven (convection setting with bottom heat element) at 180°C for a good 30 min. Serving suggestion: Cut the tart into six or eight pieces like a cake.