Place the raisins in a small bowl and cover them with boiling water. Let the raisins soak for 15 minutes until soft, and then drain them and pat dry with a paper towel. Set aside until needed.
Meanwhile, in a large mixing bowl, combine the egg yolks, lemon zest, vanilla extract, sugar. Whisk until the mixture is combined. Then add the tvorog cheese, butter, raisins, and semolina. Mix well with a spatula until the cheese mixture is smooth and creamy.
Using a stand or hand mixer, whip the egg whites with a pinch of salt until soft peaks.
Gently fold in the egg whites into the cheese mixture, carefully mixing it in with a spatula.
Preheat the oven to 325F. Spray a 9-inch x 5-inch loaf pan with baking spray. Scrape the tvorog mixture into the pan and transfer it to the oven. Bake the cheesecake for 75 min, rotate the pan 180 halfway through baking. Turn the heat off when the cheesecake is golden brown on top but still slightly jiggly in the center.
Let the cheesecake to cooldown in the oven for 20 min, with the door halfway open. This will prevent it from collapsing in the middle. After 20 min, remove tvorog zapekanka from the oven and let it completely cool on a wire rack.