Tarte à l'oignon

Combine 250 g flour, 100 g butter, 50 g cold water, and 5 g salt to form a smooth dough.

Roll out the dough and press it into a tart pan, then chill for 30 minutes.

Sweat 1000 g of thinly sliced onions in 75 g of butter over low heat until soft and translucent.