For the Spinach and Tomato Lasagna, thaw the spinach leaves overnight in the refrigerator. Cut the tomatoes into thin slices. Preheat the oven to 190 degrees.
Line the bottom of a roaster (or an oven dish – but grease it first) with lasagna sheets. Spread a third of the spinach leaves on top, then place a third of the tomatoes on top of the spinach and sprinkle a third of the gratin cheese on top.
Add a little salt, a little pepper and start again – lasagna sheets – spinach – tomatoes – gratin cheese – add a little salt, a little pepper and repeat again.
Bake in the oven on the middle shelf for about 45 minutes until the cheese has a nice golden color.