Preheat oven (electric cooker: 225°C/circulating air: 200°C/gas: level 4). Unroll the tarte flambée dough together with the baking paper on a baking tray. Mix sour cream and horseradish, season with salt and pepper.
Spread the dough with it. Pre-bake in a hot oven for 12-15 minutes.
In the meantime, wash the dill, shake dry and finely chop the flags. Take the tarte flambée out of the oven, cover with salmon and sprinkle half of the dill on top. Bake at the same temperature for 2-3 minutes.
Take out and loosely spread the trout caviar on top. Sprinkle with remaining dill. Cut the tarte flambée into quarters and serve.