Preheat oven to 350℉. Lightly grease and flour two 9-inch cake pans. (This cake can also be made in a 9x13, see notes below). For best results, cut a circle of parchment to place in the bottom of each pan. Set aside.
Combine the flour, salt, baking soda, and cinnamon in a medium bowl. Set aside.
In a large bowl, beat the eggs, sugar, oil, buttermilk, and vanilla on high speed until smooth. Add the dry ingredients and beat on low speed until combined. Fold in the carrots. Fold in the pineapple, coconut, and pecans (if using). Divide the batter evenly among the pans and bake for 25-30 minutes or until a pick inserted into the center of the cakes comes out with only moist crumbs attached.
While the cakes are baking, prepare the buttermilk glaze. Combine sugar, baking soda, buttermilk, butter, corn syrup, and vanilla in a large pot (think soup pot or Dutch oven- it will expand!) and bring to a boil over medium heat. Boil, stirring constantly, until the syrup is caramelly and golden, about 5-8 minutes. Remove from heat, stir in vanilla, and set aside.
When the cakes are done baking, drizzle the glaze over the warm cakes (still in the pans). You'll want to do it slowly and let it soak in just a bit at at time. Note: This is quite rich and decadent, so feel free to put on a little less glaze, or save some for drizzling over the top of the finished cake. It's flexible!Your cakes do not need to be swimming in glaze :) Cool completely on a wire rack. When the cakes are cool, remove them from pans. Yes they will be a little sticky so just be gentle!
When cakes are completely cool, prepare the cream cheese frosting. Beat cream cheese and butter until smooth and creamy. Add cream cheese and vanilla and whip until smooth.
If making a layer cake, tear four thin strips of parchment or wax paper or aluminum foil and make an overlapping square on the serving plate. This is to protect the serving plate from frosting. Place one layer on top of the square with the parchment strips sticking out. Spread some frosting on the bottom layer of the cake. Place other layer on top of the frosted layer. Frost the entire cake with cream cheese frosting and decorate with coconut and chopped pecans if desired. Pull out the parchment strips for clean presentation.
Store in refrigerator. When ready to serve, leave at room temp for about 30 minutes before serving.
Notes
This cake has many steps and can be overwhelming to make all at once. The cake layers can be made in advance and refrigerated or frozen before icing the cake.
The glaze recipe makes just under 1 1/2 cups of glaze. As it is written, the recipe calls for this to be split amongst the cakes. It is quite rich and decadent, so feel free to put a little less, or save some for drizzling over the top of the finished cake. If you'd like to skip that step, the cake is still delicious without it!
You may also bake this cake in a 9x13 pan. It will most likely take 30-40 minutes. Watch for it to be set and have only moist crumbs attached when poked with a toothpick. When making a 9x13 size, I find that 1/2 the frosting recipe is the perfect amount for me. I also do not use all of the glaze on the cake. I've skipped it entirely, or used about half for glazing and half for optional drizzles on top.