In a large mixing bowl, cream sugar and butter until blended. Add one egg at a time, mixing between each addition.
Add vanilla extract and sour cream. Blend until incorporated.
Add all dry ingredients, mix until fully combined and the batter is smooth.
In a large bowl, with 1 Tbsp of flour, lightly coat the frozen cranberries in flour. This method will prevent the berries from sinking to the bottom of the loaf during baking as the flour coating adds friction against the batter.
Gently fold the cranberries into the batter using a spatula.