Grate or crumble the cheese and add it to a large bowl.
Mix in the egg, sugar, lemon zest and baking soda
Add the flour and knead until you get a dough that is still very slightly sticky. Shape it into a ball.
Let the dough to rest for about 15-20 minutes. Divide the dough into 4 smaller balls.
Each ball will then be divided into 2, we will need about 3/4 of that dough for the main doughnut and 1/4 for the small ball that goes on top.
We will then have 4 doughnuts and 4 small balls in total.
Heat up a large pan and add the oil. Add one doughnut and one ball and let them fry on each side for about 2 minutes until golden. Remove with a spatula and transfer to a plate with kitchen towel to absorb some of the excess oil. Repeat with the remaining doughnuts and balls.
Serve with sour cream and any jam you prefer.