Assuming you do not start off from purchased almond meal, but start from raw almonds, blanch the almonds in boiling water for 30 seconds. Thereafter separate the almonds from the hot water using a sieve or a colander or the like. Discard the water
Let the blanched almonds cool down
Meanwhile whisk the eggs and grate the zest from the lemon's peel
When sufficiently cooled, take the skin off each nut. This should be an easy job, Discard the skins
Air dry the almonds by spreading them on kitchen paper
When sufficiently dry, place one third on a baking sheet or oven tray, covered with some parchment paper and roast in a preheated oven at 355 F (180 C) for 12-15 min
Thereafter take them out and let them cool down
When the nuts are cooled down enough, place all nuts in the kitchen blender and grind them. Do not overdo it as we want to prevent almond oil separating out (the early visible signs of this is almond meal sticking high to the wall of the container
Then in a bowl mix the sugar with the almond meal and add the lemon zest, salt (if using), lemon juice (if using), and the bitter almond extract (if using) and part of the eggs and bring together. Kneed a bit until the mixture feels pliable and the sugar grains cannot be independently noticed when tasting. Add all the egg mixture to achieve this, if need be.
Roll into a roll and tightly wrap it in plastic foil. Store it overnight in the fridge to let the taste develop
The next day use it, or store for another week in the fridge or 6 months in the freezer.