Preparation of the tomato sauce
Slice the onions and brown them in a frying pan. Add the can of crushed tomatoes and 2 good tablespoons of olive oil, the cinnamon, the honey, salt, pepper, and let reduce everything for 25 minutes over medium heat.
We should obtain a sauce, which can be homogenized with 1 small can of ready-made tomato coulis.
While the sauce simmers…

Preparing the eggplantsCut the eggplants into rounds (without peeling them), salt generously, and let them drain while you make the potatoes
(Tip for draining the eggplants: in a dish, alternate a layer of salted eggplant slices and a layer of absorbent paper or leave them in a colander.)

Preparing the potatoes
Peel your potatoes and precook them for 5 to 10 minutes in a pan of boiling water (5 minutes for small potatoes, 10 minutes for large ones). Cut the potatoes into thin rounds.
Arrange the potato rounds in the bottom of a fairly high, oiled gratin dish (this will be the dish in which you will cook your moussaka). Sprinkle the potatoes with a little (3 tablespoons) of the juice released by the simmering tomatoes.
Place the potato dish under the grill for 5 to 10 minutes depending on your oven, so that they brown.

The eggplants:
Put the eggplant slices in the pan over high heat to grill them a little on each side, set aside.