To Make the Batter with a Stand Mixer:

1. Preheat oven to 325°F.  It’s highly recommended to use an oven thermometer for this recipe, since proper oven temperature will impact the outcome of your cake.
2. Combine the flour, baking soda, cream of tartar, and cinnamon in a medium bowl.
3. Sift the flour mixture into another medium bowl.  Add kosher salt to the flour mix and whisk to combine.
4. Place the room temperature butter and cream cheese in the bowl of your stand mixer.  Mix on low speed until smooth.  (30 seconds)
5. Slowly add the granulated sugar and mix on medium speed until the mixture is light and fluffy.  (5-10 minutes)
6. Add eggs, one at a time, mixing for at least 45 seconds after each addition.  Scrape the sides and bottom of the bowl as needed (I usually scrape the bowl after the third and sixth egg).  Don’t skimp on this step because it helps the cake rise!  (7 minutes)
7. Add vanilla extract and mix until thoroughly combined.  (1 minute)
8. Add half of the flour mixture and mix on low speed until combined.  (30-45 seconds)
9. With the mixer on the lowest speed, add all of the buttermilk and mix until just combined.  (~1 minute)
10. Add the second half of the flour mixture and mix on low speed until almost combined.  Stop mixing just before the mixture is fully together.  (~1 minute)
11. Using a rubber spatula, fully scrape the sides and bottom of the mixing bowl.  Then, stir the batter until it is smooth and consistent.  Make sure to fully scrape the bottom of the bowl during this step!
12. Grease a 10-12 cup bundt pan with the remaining butter and flour and place the batter in the pan.

To Make the Batter with a Hand Mixer:

1. Preheat oven to 325°F.  It’s highly recommended to use an oven thermometer for this recipe, since proper oven temperature will impact the outcome of your cake.
2. Combine the flour, baking soda, cream of tartar, and cinnamon in a medium bowl.
3. Sift the flour mixture into another medium bowl.  Add kosher salt to the flour mix and whisk to combine.
4. Place the room temperature butter and cream cheese in a large mixing bowl.  Mix on low speed until smooth.  (~1 minute)
5. Add half of the sugar and mix until the sugar is just incorporated.  (~30 seconds)
6. Add the second half of the sugar and mix on medium speed until the mixture is light and fluffy.  (7-12 minutes)
7. Add eggs, one at a time, mixing for at least 1 minute after each addition.  Scrape the sides and bottom of the bowl as needed (I usually scrape the bowl after the third and sixth egg).  Don’t skimp on this step because it helps the cake rise!  (7 minutes)
8. Add vanilla extract and mix until thoroughly combined.  (1 minute)
9. Add half of the flour mixture and mix on low speed until combined.  (30-45 seconds)
10. Add all of the buttermilk and mix on lowest speed until just combined.  (~1 minute).
11. Add the second half of the flour mixture and mix on low speed until almost combined.  Stop mixing just before the mixture is fully together.  (1-2 minutes)
12. Using a rubber spatula, fully scrape the sides and bottom of the mixing bowl.  Then, mix the batter until it is smooth and consistent.  Make sure to fully scrape the bottom of the bowl!
13. Grease a 10-12 cup bundt pan with the remaining butter and flour and place the batter in the pan.

To Bake the Cake:

1. Bake the cake at a true 325°F for 60-70 minutes, or until an instant read thermometer reads 210°F-215°F.  My preferred internal temperature for this cake is 212°F.  Alternately, the cake is done with a toothpick inserted into the center comes out clean and a fingerprint indentation bounces back.
2. Allow the cake to rest for ten minutes while you make the simple syrup.

To Make the Cinnamon Simple Syrup:

1. Combine sugar, water, salt, and cinnamon in a small saucepan and bring to a boil.  Stir occasionally until the sugar is completely dissolved.
2. Remove the simple syrup from the heat and add vanilla. Stir until incorporated.
3. After allowing the cake to rest for ten minutes, invert it onto a cooling rack and carefully remove the bundt pan.
4. Using a pastry brush, gently brush the cinnamon simple syrup over the entire cake.
5. Allow the cake to cool completely.  (3-5 hours)

To Make the Snickerdoodle Glaze:

1. Combine the confectioner’s sugar, vanilla, cinnamon, salt, and whole milk (3 tbsp)  in a medium bowl.  (see note about glaze, below.)
2. Stir with a spoon until nearly combined, then add 1 tbsp of heavy cream.  Stir until smooth.  The glaze will be thick but should be pourable.
3. Final glaze should have the consistency of thick honey, and you should just be able to pour it.  Add whole milk, one teaspoon at a time, if the original glaze is too thick to pour.
4. Using a spouted measuring cup, spoon, or squeeze bottle, drizzle final glaze over the cake.  For this cake, I used a spouted measuring cup.
5. If necessary, use a spoon to help the glaze fall over the sides of the cake.
6. Allow the glaze to set for five minutes, then gently sprinkle decorating sugar (if using) to finish.

To Store:

This cake can remain on a countertop overnight, or it can be stored in a refrigerator for up to a week.