Preheat your oven to 350ºF. Grease and lightly flour a standard 12-cup bundt pan, and set it aside. Into a medium-size bowl, sift (yes, sift!) the flour, xanthan gum, cornstarch, salt and baking soda, and whisk to combine well. Set the bowl aside.

In the bowl of a stand mixer fitted with the paddle attachment, or a large bowl with a handheld mixer, place the shortening, sugar, vinegar, vanilla and 1 tablespoon of the water, and beat on high speed until light and fluffy. (If you are using oil, place the oil, sugar, vinegar and vanilla in a blender and blend until very well-combined.)

To the beaten shortening and sugar mixture, add the dry ingredients and the remaining water in 3 to 4 batches, beginning and ending with the dry ingredients and beating until just combined in between. (If you are using oil, add the oil and water mixture to the dry ingredients and beat until just combined.) The batter should be soft, and relatively fluffy. (If using oil, the batter will be heavier.)

Pour the cake batter into the prepared bundt pan and spread into an even layer. Place in the center of the preheated oven and bake until a toothpick inserted halfway between the center of the bundt pan and the edge comes out clean (about 40 minutes). Remove from the oven and allow to cool in the pan for 10 minutes before turning out onto a wire rack to cool completely.

To make the cream cheese glaze, place the cream cheese, confectioners’ sugar, salt, vanilla and 1 tablespoon of water in the clean bowl of a stand mixer fitted with the paddle attachment (or a large bowl with a handheld mixer). Beat on high speed until very smooth and thick. You can add more water by the 1/2-teaspoonful if it seems too thick to spread. Spread the glaze on top of the cooled cake, then allow it to set at room temperature until mostly firm (it won’t dry completely). Slice and serve.