Dice the onion and fry with the minced meat, season with salt and pepper. Add the frozen spinach. Dice the feta cheese and add to the pan. When all the ingredients are hot and melted, add the sour cream.
Now alternate the lasagne plates with the spinach mixture in a baking dish. The last layer should be spinach. Cut the tomatoes into slices and place on the lasagna.
Bake in a preheated oven at 200 ° C for approx. 40 minutes.