Separate the eggs. Beat the whites with a pinch of salt until fluffy. Start adding sugar in batches.Beat the yolks with a fork and add them to the whites. Mix together. Add the lemon zest, vanilla and melted butter.
Mix the flour with baking powder and sift over the batter in batches. Incorporate the flour very slowly with a spatula or hand whisk to avoid losing too much air from the batter.Line the baking pan with parchment paper and transfer the batter. Add sour cherries on top and preheat oven to 350F (180C).
Bake for about 50-55 minutes until golden brown and a toothpick comes out clean. Let it cool. Dust with icing sugar and cut into bars or squares.Serve with your favorite beverage or coffee.