Preheat oven to 350°.

Cover the prunes with freshly boiled water and let them soak until soft a plump, about 30 minutes. Then drain them, squeeze out all the liquid and set aside.

Line a 15″-x-10″ baking sheet with parchment paper and grease with cooking spray.

In a large bowl, beat egg whites with sugar and salt until soft peaks. Add the yolks and beat until incorporated. Add the honey, cinnamon, and baking soda drizzled with lemon juice. Mix well to combine. Then sift in the flour and carefully mix with a spatula with a mixer on low settings.

Pour the batter on greased parchment paper and carefully spread it with a spatula to form an even layer. Bake for 20 to 25 minutes until the cake is golden brown and cooked through.

Remove the cake from the oven and move it onto a large kitchen towel. Cover the cake with another piece of parchment paper sprayed with cooking spray and tightly roll. Secure the roll with a kitchen towel and let it cool to room temperature.

Meanwhile, whip the heavy cream with sugar and vanilla extract until soft peaks. Whisk in the sour cream. Refrigerate until needed.

When ready to assemble the cake, carefully unroll it and remove the top layer of parchment. Spread a thick layer of chilled sour cream frosting, leaving about 1 cup of frosting for decoration. Place a row of prunes 1 inch away from the lower edge of the cake. Gently roll the cake and peel off the bottom layer of parchment. Decorate the top of the roll with the remaining frosting and dust with cinnamon. Refrigerate the cake for at least 4 hours before serving.