Generously grease four 9 x 5 x 3-inch loaf pans with 1 to 2 teaspoons of the pound of butter then line the pans with parchment paper, or brown paper cut from grocery bags.
In a very large mixing bowl, cream the soft butter and sugar with an electric mixer on high until fluffy (about 5 minutes).
Separate the eggs so the yolks are in one bowl, the whites in another.
Beat the egg YOLKS and lemon extract for about 2 minutes, until smooth and frothy (don’t be alarmed by the amount of extract, it’s a lot and it’s okay).
Add the egg yolk and lemon mixture to the large bowl mixture of butter and sugar. Continue mixing to incorporate.
In a separate bowl, mix fruit and nuts with half of the flour and the salt; add this to the mixture in the big bowl. Stir in with a large wooden spoon.
Add dissolved soda and pickled fruit juice (or your choice of substitutes see NOTE 1, then the remaining flour. Stir to incorporate. The batter will be stiff.
In a separate bowl, beat the egg whites until soft peaks form. Fold the beaten egg whites into the large bowl mixture with a large spoon, until well incorporated.
Divide between prepared pans until each is about 3/4 full. Place pans in a COLD oven set to 250 F. Bake for about 2 hours or until golden brown. Test for doneness (see NOTE 4). Do not overbake! Cool in pans on a cooling rack.
Once cool, remove from pan(s) and wrap tightly in plastic wrap and then foil. Store in a cool place or the refrigerator for up to 4 weeks. See NOTE 3.