Using a whisk attachment, whisk egg whites and lemon in a stand mixer or with a hand mixer until stiff peaks form.
In a large bowl mix together the almond flour, cocoa powder, and caster sugar. Using a fine mesh sieve, sift the mixture to remove any lumps into another large bowl. This will ensure the ingredients are well incorporated.
Fold in one cup of the dry ingredients into the whipped egg whites. Add the vanilla extract and more dry ingredients. Continue to add dry ingredients, slowly adding in the almond extract/amaretto liqueur until all ingredients are added. A sticky dough will form.
Preheat the oven to 325°F. Prepare two cookie sheets with parchment paper or a silicone baking mat.
In a small bowl, combine remaining caster sugar and powdered sugar and mix.
Using a small cookie scoop, roll scant tablespoon sized balls of cookie dough. Coat these by rolling in the prepared sugar until completely covered.
Place dough balls about one inch apart on the prepared cookie sheet, these cookies do not spread while baking.
Place prepared cookies into the refrigerator for about 15 minutes. Once removed from the fridge, cover the cookies with a piece of parchment paper and using another cookie sheet, gently press down on the surface of the cookies to slightly flatten. This will improve the cookies crinkling and cracking while baking.
Bake in the oven for 15 minutes. Remove and allow to cool for 5 minutes prior to moving to a cooling rack to cool completely.
Store in an airtight container for up to a week.