Preheat oven to 350 F. Spray the inside of your bundt pan generously with oil. No need to flour the pan. However, if you sprinkle sugar into your oiled pan it will create a pleasant "crust" on your cake. I didn't do that for this recipe though.
Measure out the 3 cups of flour into a bowl. Remove 3 tablespoons of the flour. Add in the listed 3 tablespoons of corn starch. You just made your own cake flour!
Measure 1 cup of oatmilk or other non-dairy milk. Add 1 Tbl of apple cider vinegar and mix. Let stand while you prepare the other ingredients. You just made vegan buttermilk! Look at all the things you're making today!
Whisk together all of the dry ingredients. For cake making I prefer to sift the dry ingredients together ensure leaveners are fully incorporated and there are no clumps.
Using the paddle attachment on your stand mixer mix the room temperature butter into the dry ingredients. It should look like sand after 2-3 minutes of mixing.
Add the apple sauce, vanilla, bourbon. Mix until fully incorporated.
Add in the buttermilk. Mix until batter is smooth. Don't be afraid to turn up the speed.
Pour into greased bundt pan. Bake on middle rack for 45-55 minutes. Inserted toothpick or cake tester should come out clean.
In the last 10 minutes of baking make your glaze. Heat all ingredients in a sauce pan while stirring. When the glaze starts to bubble on the edges turn the head down to medium. Heat while stirring for 5 minutes. Turn off heat and set aside for the next step.
Leave cake in pan. Using a chopstick or similar item poke holes in the cake bottom. Be careful to not go all the way through. The holes only need to be an inch deep.
Spoon 3/4 of the warm glaze into the holes. Avoid simply dumping the glaze into the pan. You want the hot glaze to soak into the cake.
Let cake sit in pan for 30 minutes. Carefully invert onto cake stand or plate. Drizzle the remaining glaze over the top of the cake.
A bundt cake is always best the next day. These dense cakes get better as the flavors temper and infuse.