Pre-heat your oven to 300 degrees F. Line a baking sheet with parchment paper and flour lightly, and set aside. In a large mixing bowl beat together the butter and sugar until it is light and fluffy. Add in the eggs one at a time, mix well then add in the vanilla. Mix rogether the flour, baking powder, salt and lemon zest, whisk together to blend and slowly add to the egg mixture. Once the dry ingredients have fully blended with the wet ingredients remove the bowl from the mixer and fold in the cherries and almonds.
The dough will be very sticky so with floured hands, divide the dough in half on he prepared baking sheet. roll the dough into two even logs measuring 14"x4": the logs should be at least 3" apart. Beat the egg white with just a splash of water and brush it over the two logs, then sprinkle hem with the course sugar. Bale for 30 minutes.
Remove the biscotti from the oven and let them cool directly on the baking sheet for about 10 minutes. Transfer the logs onto a cutting board and clice into 3/4" thick slices. Place the slices back onto the baking sheet and bake for additional 10 minutes, flip the biscotti over and bake again for another 10 minutes or until they begin to turn golden brown.
Notes: If you like a softer biscotti bake for 5 minutes on each side. A good course sugar to use is "Sugar in the Raw", which is also known as: Turbinado Sugar.