Sticky Grapefruit Honey Squares

These cakes are dense and sticky, a homage to the honey-drenched cakes I enjoyed from many Cypriot relatives and family friends in my youth. Theirs were studded with crumbled walnuts and pistachios; I have opted to spike mine with the lip-smacking tartness of tinned grapefruit. The honey syrup is mandatory; the cake just isn’t the same without it.