Preparing the dough:
Before you start, make sure all the ingredients are at room temperature.
Whisk the softened butter and sugar until they become fluffy. Add the eggs and thoroughly blend them in. Combine the baker's ammonia and milk, then add this mixture to the egg mixture.
In a separate bowl, mix the flour and grated lemon zest together. Gradually add this mixture to the egg mixture. The resulting dough should appear somewhat oily and should not stick to your hands. If needed, you can incorporate an extra tablespoon of flour.
Place the mixture in the fridge for a few minutes while you prepare for the next steps.
Preheat your oven to 360°F (180°C). Prepare a quarter-sized cookie sheet pan or a similar-sized baking pan.
Grease the outside bottom of the pan generously with butter and dust it with flour. This step is necessary only before the first layer.
You'll be creating six layers, possibly seven if you gather enough small dough scraps from the initial six layers.
Take the dough from the fridge and place it on a floured work surface. Knead the dough again and divide it into six equal pieces, placing the rest in separate ziplock bags.
Roll out each piece thinly, less than 1/8-inch thick, ideally forming a rectangular shape close to the dimensions of your pan. This may take a little practice.
Carefully transfer each rolled-out dough layer onto the cookie sheet pan, then trim the edges with a small knife to achieve an almost perfect rectangular layer of dough. Save any extra dough scraps.
Bake each layer for 10 to 15 minutes until the edges barely darken.
After baking, designate an area where you will stack your cake layers. You'll need a large surface to press them with a heavy board until they cool completely, preferably overnight.
Begin preparing the filling after your cake layers have completely cooled, preferably on the same day or even the following day.