Dissolve the yeast and 1 tbsp sugar in a little less than a cup of lukewarm milk (220ml). Stir then let stand for 8-10 minutes.
In a bowl, stir together flour and salt. Add the butter and the milk mixture. Knead with a wooden spoon first then by hand or in a stand-in mixer until dough comes together. Knead the dough for 6-8 minutes. Add a little bit of flour if the dough seems too sticky.
Place the dough in a lightly oiled bowl, cover with plastic wrap and place somewhere warm for an hour to let rise
In the meantime, cut the nectarines in two. Remove the pit and cut the nectarines into small dices. Dice the cold butter as well
Grease and dust a 9×5 loaf pan with flour
Once the dough is ready, punch it down and knead again for a minute or two. Roll out the dough into a 20×12 inch rectangle. Brush the rest of the milk and the sugar on the surface. Finally, spread out the nectarines and butter dices on the dough (press gently)
Cut the dough into squares of the same size (they should fit into the loaf pan – basically like a toast). Line up each square in the pan (vertically). Cover again with a clean dishcloth and let it rise again for 30 minutes.
Pre-heat the oven to 350F
Whisk the egg and brush it over the dough. The cake needs to bake for about 35-45 minutes. After 20 minutes, cover with aluminium foil and bake for another 20 minutes. The top should be golden
In the meantime, toast the almond slivers in a pan. For the glaze, whisk together lemon juice and powder sugar
Remove the cake out of the pan, brush with the glaze and sprinkle with the almond. And it’s ready to serve!