Defrost the spinach, place in a baking dish. Halve the tomatoes and mix with the spinach.
Mix a sauce from the horseradish, yoghurt, broth, salt and pepper, pour over the vegetables. Spice it up, the horseradish is swallowed well by the spinach.
Cut the trout into smaller pieces and place on top of the vegetables.
Place in the oven at 200 ° C for about 20 minutes, until it is nice and hot and the horseradish and trout aromas are well distributed.