Peel and wash the potatoes and cook them in salted water for about 20 minutes. Drain potatoes and let them evaporate on the switched off hotplate. Wash marjoram, dab dry, pluck leaves from the stalks and chop finely, possibly except for a few for sprinkling.
Grate cheese. Press potatoes through a potato ricer. Add lemon zest, marjoram, parmesan, ground almonds and eggs to the potatoes. Melt 50 g butter, add it to the potatoes and knead everything into a smooth dough.
Season with salt and pepper. Line a tart mould with lift-off base (24 cm Ø) with baking paper and place the ham in the mould so that the slices hang over the edge. Pour the potato mixture into the mould and smooth it down.
Fold the overhanging ham over the dough. Spread 20 g butter in flakes on top, sprinkle almond flakes on top. Possibly sprinkle some marjoram on top. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 35-40 minutes, cover with foil if necessary.
Remove the potato tart, let it cool down briefly and cut into pieces.