Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Peel, wash and coarsely grate potatoes. Stir in 1 egg and flour. Season with salt and pepper, mix well. Squeeze the mixture well in a sieve.
Grease a springform pan (26 cm Ø) with oil. Pour the hash mixture into the springform pan and press it down to an even base and rim. Pre-bake in a hot oven on the lowest shelf for about 20 minutes.
Peel onions and garlic. Dice onions and chop garlic finely. Fry bacon in a large pan (with lid) without fat in portions until crispy. Take out and drain on kitchen paper.
Fry onions and garlic in hot bacon fat. Add frozen spinach and 5-6 tablespoons of water. Season with salt, pepper and nutmeg. Bring to the boil, cover and steam over medium heat for about 15 minutes.
Then drain it.
Meanwhile wash and halve the tomatoes. Crumble the feta. Well 2⁄3 with milk, 2 eggs, little salt and pepper with the hand blender. Coarsely crumble the bacon, approx. 2⁄3 Mix the bacon and the feta egg cream with the spinach.
Spread the spinach on the Rösti base. Spread the tomatoes, remaining bacon and remaining feta on top. Bake in the oven at the same temperature for about 45 minutes.