For the most tender cake, use cake flour!
Cake flour has a lower protein content than all-purpose and will result in a softer cake.
Add a couple TBS of cornstarch to AP flour if you do not have cake flour.
The reverse-creaming method mixes the flours, sugar, and butter at the beginning.
It coats the butter and results in less mixing.
Ultimately, this makes a more tender cake.
To prevent your bundt cake from sticking, grease and flour your pan well.
I like to use non-stick spray to evenly coat the pan and its crevices and then dust it lightly with flour.
Bundt cakes contain a lot of sugar. Offset the sweetness with lots of lemon zest and juice, plus the tanginess of buttermilk, and sourdough starter in this recipe.