In a bowl, combine tomato sauce, olives and water and mix well.
In another bowl, combine ricotta cheese, lemon juice, and oregano, mix until combined.
Prepare your lasagna dish. Spread 1/2 cup of sauce on the bottom of the dish. Arrange half of your lasagna noodles over the sauce, top noodles with 1/2 ricotta mixture, 1/2 cup of mozzarella, 1/2 of crumbled feta and spinach. Continue layering all remaining ingredients in the same order.
Pour all remaining sauce on top. Cover with plastic wrap and transfer to the fridge overnight.
On the next day uncover your lasagna and bake for 35 minutes. Take out of the oven, sprinkle with the remaining cup of mozzarella and return back to the oven for an additional 20 minutes or until cheese is melted and golden.
Let sit 15 minutes before serving.