Preheat the oven to 200C / 392F and grease a 20cm x 20cm deep casserole dish.
Slice the eggplant as thinly as you can, and lay the pieces out on a cookie sheet. Brush with olive oil and bake for 15 - 20 minutes, flipping once, until tender. Alternatively, you could grill them in batches in a frying pan.
While the eggplant is baking, in a large bowl combine ricotta, drained spinach, parsley, basil, salt, pepper, nutmeg and lemon. Mix thoroughly to ensure even distribution of spices.
In the prepared casserole dish, begin with a layer of cooked eggplant, then top with 1/3 of the ricotta mixture. Repeat the layers of eggplant and ricotta until all ingredients are used up.
Top with the passata and sprinkle on the grated cheese. Cover with tin foil and bake for 30 - 40 minutes until piping hot through, removing the tin foil for the final 10 minutes so the cheese gets nice and crispy.