Whisk warm butter (I whipped it with a whisk) with sugar (2 tablespoons), salt and vanilla. Then add the egg and sour cream. Beat for another minute. Then add flour and baking powder. According to the original recipe, it turns out 300 grams of flour, but it took me more. Instead of baking powder, I take baking soda and citric acid. Knead the dough that has not cooled down, form a ball, wrap it in a film and put it in the refrigerator for 2 hours.