For the most authentic flavor, I recommend using regular cocoa powder. But for a darker color and richer flavor profile, try the Special Dark cocoa, which is a blend of natural cocoa and Dutched cocoa.
Preheat your oven to 350ºF. Grease and flour a 9x13-inch baking pan.
In a large bowl, whisk together the flour, sugar, baking powder and baking soda.
In a small bowl, whisk together the soymilk, flaxseed meal, vinegar, and vanilla.
Add the buttery spread, cocoa and cola to a small saucepan over medium-high heat. Cook just to boiling, reduce the heat and stir occasionally until the buttery spread is melted. Remove from heat.
Make a well in the center of the flour and sugar mixture. Pour in the soymilk mixture followed by the buttery mixture. Whisk just until smooth and well combined.
Pour the batter into your prepared baking pan and gently smooth the top. Bake for approximately 25 minutes, checking for doneness with a wooden pick inserted in the center after about 20 minutes.
Place the pan on a wire rack and make the frosting and pour it over the warm cake. Smooth the frosting over top of cake. Garnish, if desired with the pecan halves.
Let cool completely before servings. Store leftovers covered in the refrigerator, but bring to room temperature before serving.
For the Fudgy Cola Frosting:
In a large saucepan over medium-high heat, bring the buttery spread, cola, and cocoa to a boil. Reduce the heat to a simmer and stir occasionally until all is melted.
Remove from the heat and whisk in the confectioner’s sugar, one cup at a time, until smooth and completely incorporated. Stir in the pecans, if using, and immediately frost the cake.
Recipe by Go Dairy Free at https://www.godairyfree.org/recipes/vegan-coca-cola-cake-with-fudgy-frosting