Thaw and heat the spinach leaves in the microwave (takes about 8-10 minutes).
At the same time, cut the potatoes into cubes and cook them (I cooked them in the microwave, it took 8 minutes). So if you have the right accessories, you save time. Cut the tomatoes into slices.
Take a baking dish or a microwave-safe glass dish and add the spinach, layer the potatoes on top and finally top the tomatoes on top. Possibly Cut a slice of processed cheese into small pieces and place over the tomatoes.
Put the whole thing in the oven (200 ° C) or in the microwave for a few minutes.