Preheat oven to 350º F. Generously spray 12-cup fluted tube cake pan with baking spray with flour.
In a large bowl, sift flour, baking powder, and cream of tartar. Add salt and mix to combine. Set aside.
In a large bowl, beat the sugar and butter until creamy and pale on medium-high speed. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. Add sour cream, milk, and vanilla and continue beating to combine.
Reduce speed to low and add the flour. Scrape down the mixing bowl with a spatula and turn the batter over several times to ensure all of the ingredients are well incorporated. Beat just until combine. Do not overmix this batter.
Pour the cake mixture into the prepared pans. Bake for 50 - 60 minutes, or until a skewer comes out clean when poked in the center.
Once done, remove from the oven and allow to cool for 10 – 15 minutes inside the pan. Then, invert the slightly cooled bundt cake onto a wire rack or serving dish. Allow cooling completely before slicing.
Glaze: whisk confectioners' sugar and 3 tablespoons of milk together. Add extra milk, 1 tablespoon at the time, as needed.
Drizzle glaze over cake, sprinkle with your favorite sprinkles, if desired, and serve.