In a bowl, mix 4 egg yolks with the flour, 2 tablespoons of oil and 100 ml of lukewarm water to form a homogeneous dough and season well with salt and pepper.
The dough should be smooth and at the end dusted with enough flour until it no longer sticks to your hands. It is best to mix the ingredients in one piece in a food processor.
Roll out the dough thinly with a rolling pin on baking paper and brush with creme fraîche with the back of a spoon.
Peel 2 small red onions and cut into rings. Distribute this evenly on the creme fraîche. Then bake the tarte flambée in the oven on the middle rack for 15 minutes.
During this time, remove the skin on the underside of the Stremel salmon. Pluck the salmon into fine pieces and set aside.
Wash the arugula and place in a large bowl. Mix the honey, mustard, vinegar and 1 tablespoon of cold water in a small bowl. Pour the vinaigrette over the rocket and mix well.
After the baking time, take the tray out of the oven and cover evenly with the Stremel salmon. At the end, spread the rocket with the dressing over the tarte flambée and serve.