Preheat your oven to 350°F (175°C) and grease an 8×8-inch baking dish.

Cream the softened butter and sugar together until light and fluffy, about 3–5 minutes.

Add the egg yolks one at a time to the creamed mixture, mixing well; then fold in the lemon zest and juice.

In a separate bowl, whisk the flour, baking powder, and salt, then mix gently with the wet ingredients, alternating with warm milk.

Whip the egg whites to stiff peaks and gently fold them into the batter.

Pour the batter into the greased baking dish and bake for 35–40 minutes until golden brown on top.

Allow the cake to cool for at least 30 minutes before dusting with powdered sugar or garnishing with fresh berries.