Slice the zucchini into quarter inch lengthwise planks, salt both sides generously, and lay them on racks or towels for 30 minutes. Blot them hard with towels; this step is the whole recipe.
Meanwhile, brown the beef hard in the oil, add the onion for 5 minutes, then the garlic and oregano for 30 seconds, then the tomato sauce and salt. Simmer 15 minutes until thick; watery sauce plus watery squash is how lasagna drowns.
Stir the ricotta with the egg and half the parmesan.
{'In a 9 by 13 dish, layer': 'a thin coat of meat sauce, zucchini planks, half the ricotta mix, a third of the mozzarella, then repeat, ending with sauce, the last mozzarella and parmesan on top.'}
Bake at 400F, uncovered, 40 to 50 minutes, until bubbling hard at the edges and deeply browned on top.
Rest 15 minutes before cutting. Cut early and it slides; rested, it slices.