I developed it when I was trying to find for a use for a bunch of slivered almonds and jam. I remembered seeing similar tarts when I traveled to England last summer with a friend, and decided to use ingredients on hand, including rice flour and spelt flour, to recreate the tasty treat and keep suitable for those sensitive to gluten. —maiah03
For the tart dough: mix flour, butter and sugar in a mixer or processor until it resembles coarse crumbs. Add the egg yolk and 1 to 2 teaspoons (or more if needed) of ice water until dough comes together. Wrap in plastic wrap and chill in the fridge at least 35 minutes.
Preheat the oven to 350. Roll out dough when ready, trimming as needed to keep it a circle, and lay inside a tart pan. Crimp edges and poke the dough with a fork several times. Cover with tin foil and bake 20 minutes or so until lightly backed. Gently push center of tart dough down to flatten if necessary halfway through. Brush with the egg white and bake for another 3-4 minutes without the foil.
Once crust has cooled slightly, mix jams together and spread in an even layer over the crust.
Beat butter and sugar together for the top layer. Add the beaten eggs and yolk, and gradually stir in the almonds. Spread this mixture over the jam layer carefully. Bake for 15-20 minutes.
Spread the slivered almonds on top, and bake another 12-16 minutes or until it is set and the slivered almonds are browned. Let cool, garnish with powdered sugar if desired.