The cheese is kind of "trappista cheese" ( https://en.wikipedia.org/wiki/Trappista_cheese ), which has a shape of "circle sect based prism".
For simplicity it has a height equal to the radius of the base circle. And beeing a quater of a cheese, it has a 90 degree angle at the center of the base circle, because in fact it is a quarter of a cylinder.
HINT.
The sum of the surfaces of the two halves will total the surface of the original piece plus twice the cutting surface. So, the question becomes simply: how to cut this into two halves with the minimal cutting area?