It doesn't need to be lemon syrup.

不需要一定是柠檬糖浆。

You basically make a lemon syrup and you pour it into the sponge whilst it's hot, and it absorbs and makes the whole thing so unctuous.

制作柠檬糖浆，趁热倒在海绵蛋糕上，它会被吸收，让整个蛋糕变得油滑。