Beat the eggs with melted butter and lemon juice until you get a soft emulsion.
Combine all the dry ingredients and start adding them to the egg-butter mixture spoon by spoon and mix with a whisk. At this point start mixing with your hand.
Let the dough sit in the refrigerator for 10 minutes.
Using your hands, take about one teaspoon of batter and roll into a ball. Place each ball 2 cm apart from each other on a baking sheet, lined with baking paper.
Preheat the oven to 180ºC or 350º F. Bake the cookies for exactly 8 minutes so that they don't get dark.
Once the cookies are cool, take a sharp knife, cut in a circle on the bottom of each of them, being careful not to poke through the other side. Scoop out the insides, saving the crumbs in a separate bowl. (this is needed for the filling)
Mix the cookie crumbles with walnuts and add the rest of the filling ingredients. The filling should be moist, so feel free to add water if it appears too dry.
Squeeze the raspberries and set the juice aside. You will use it for the decoration. Add the raspberry pulp to the filling mixture.
Fill each hole of cookies with the filling. Take two cookies and sandwich them together. The filling should stick. If it doesn't, add more water and mix it again.
Mix raspberry juice with the natural peach aroma in a deep plate. In another plate pour in the crystal form sweetener.
Dip each side of the cookie in the raspberry juice and then in the crystal sweetener. Place the cookies on baking paper and let them dry.
Serve and store them at room temperature. This version can last up to 4 days on room temperature, and 7 days in the refrigerator.