Heat the olive oil in a large pan. Add chopped onion and saute for 2-3 minutes. Add chopped mushrooms and saute for another 5 minutes. Add 1 cup chopped and peeled tomatoes, you can use canned tomatoes, mashed garlic cloves, chopped dill, salt, pepper and 1 tsp dry thyme. Saute for 5 minutes and then remove from heat.
Whisk 2 eggs and pour them in the pan. For the vegan version, just add psyllium husks. Mix well.
Preheat oven at 180C/350F.
Grease a 9×13 rectangular casserole dish with some olive oil.
Using a mandoline, make thin zucchini slices.
Cover the pan in one layer of zucchini slices. Add the mushroom composition and spread it evenly. Cover it with the final layer of zucchini slices.
Beat the remaining egg and put it over. Spread evenly.
Spread 5-6 tablespoons of tomato paste on top and sprinkle with 1 tsp of thyme.
Bake for 35-40 minutes at 180C/350F.
Serve with sour cream - optional.