Preheat the oven to 350F. Grease and flour a 10" (6 cup) bundt cake pan well. You can also use baking spray.
In a medium bowl, stir together the cranberries and ½ tablespoon all purpose flour to coat.
2 cups cranberries, fresh or frozen
In a medium bowl, combine the flour, baking powder and salt. Whisk to combine and set aside.
3 cups + ½ tablespoon all purpose flour, ½ teaspoon baking powder, ½ teaspoon fine sea salt
In the bowl of a stand mixer fitted with the paddle attachment, combine the granulated sugar and orange zest.
1⅔ cups granulated sugar, 1 tablespoon orange zest
Rub the zest into the sugar to release the oils of the zest. The sugar/zest mixture should be light orange, damp and very fragrant.
Add the butter to the sugar mixture. Beat until light and fluffy, about 5-8 minutes, scraping the bowl occasionally.
1 cup unsalted butter, room temperature
Add the vanilla extract. Add the eggs one at a time, scraping the bowl after each addition.
1 teaspoon pure vanilla extract, 4 large eggs
With the mixer on low speed, add the dry ingredients into the mixture in the three additions, alternating with the milk in two additions, beginning and ending with the flour. Mix until just combined.
¾ cup whole milk, room temperature
Beat in the sour cream until just combined.
½ cup sour cream
Remove the bowl from the mixer and fold in the cranberries.
Scrape the batter into the prepared bund pan. Bake for 45-60 minutes or until a toothpick comes out with few crumbs. Start checking the cake for doneness at 45 minutes.
Cool the cake in the pan for 20 minutes, then invert the cake onto a wire rack to cool completely.
Once cool, transfer the cake to a decorative plate or cake stand.