Lychee Butter Cake

Preheat the oven to 350 degrees F (175 degrees C). Line an 8-inch square pan with parchment paper.

Beat butter and sugar in a bowl with an electric mixer until pale and fluffy, about 3 minutes. Mix in eggs, then egg yolk, one at a time, beating well after each addition. Mix in lychee syrup and rose water until thoroughly combined, 2 to 3 minutes.

Whisk flour, baking powder, and salt together in a bowl. Add 1/2 of the flour mixture to the butter mixture and mix until thoroughly combined. Mix in remaining flour until combined and batter is smooth. Gently fold in 1/2 of the lychees.

Pour batter into the prepared pan. Spread remaining lychees evenly on top of the batter.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 40 to 45 minutes. If the edges brown too quickly, cover the pan with aluminum foil.

Remove from the oven and place on a wire rack to cool.