To Make the Batter:

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 flax meal and water thoroughly in a small measuring cup or bowl.  Set aside.
3. Combine the plant-based milk and 2 tbsp of white vinegar in another small measuring cup.  Set aside.
4. Sift the flour, baking soda, cream of tartar, salt, and cinnamon in a medium bowl.
5. Place the room-temperature plant-based butter in a large mixing bowl or the bowl of a stand mixer.  Mix on low speed until smooth.
6. Add half of the sugar and mix until the sugar is just incorporated.
7. Add the second half of the sugar and mix on medium speed until the mixture is light and fluffy.
8. Add half of the flax eggs or plant-based eggs and mix until it is fully incorporated.  Add the second half of the flax egg mixture and mix until fully combined.
9. Add vanilla extract and mix until thoroughly combined.
10. Add half of the flour mixture and mix on low speed until combined.
11. Add all of the plant-based buttermilk and mix on lowest speed until just combined.
12. 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)
13. 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!
14. 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.

To Make the Cinnamon Glaze:

1. Combine the confectioner’s sugar, vanilla, cinnamon, salt, and 3 tbsp of the plant-based milk (3 tbsp)  in a medium bowl.
2. Whisk until nearly combined, then add 1 more tablespoon of plant-based milk if necessary.  Whisk until smooth.  The glaze will be thick but should be pourable.
3. The final glaze should have the consistency of thick honey, and you should just be able to pour it.  Add plant-based 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.
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.