In a separate bowl, mix sour cream and condensed milk. Take sour cream with a fat content of 20%, but with less fat it will be perfect. Do not be afraid, if the cream turns out to be liquid, the crumb perfectly absorbs moisture, and the cream will thicken when the cake stands in the refrigerator. Condensed milk can be replaced with powdered sugar. You can also add orange zest to the cream.
Also in the season of fresh raspberries, you can add it to the cream, it will be very tasty.