Grease and flour two 8” cake pans and line with parchment paper. It’s essential so that the cake doesn’t stick.
Heat oven to 350°F/180°C.
In a small bowl or jar, add the apple cider vinegar and the soy milk together and stir to combine. It will curdle. Set aside.
Whisk together sugar, flour, baking soda and salt in a large bowl until thoroughly combined. Add milk mixture, melted butter and vanilla. Beat with an electric whisk on medium speed for about 1 to 2 minutes until everything is just combined. Scrape down the sides of the bowl and stir one more time to ensure everything is incorporated. Do not overmix.
Pour the batter equally into the cake pans and place in the middle rack in the centre of that rack. Bake for 40 minutes. Remove from the oven (test with a toothpick in the centre to ensure they’re fully cooked) and allow to cool completely in the pans.
For the Frosting
Beat the butter and vanilla for about 2-3 minutes with a stand mixer or a handheld mixer, until fluffy.
Add 1 cup of powdered sugar. Fold it in with a spatula so it doesn’t fly everywhere, then beat for about 1 minute. Add the rest of the frosting in small increments too, until fully incorporated.
Add in a 1/2 tablespoon of vegan milk at a time until it reaches your preferred volume and consistency. Add that last ½ cup if you desire.
Then beat for about 5 minutes, using the spatula to mix everything together every other minute, until the frosting is fluffy, white, smooth and creamy.
Putting it All Together
Frost cakes and decorate. The frosting will set at room temperature. Enjoy!
Place 1 of the fully cooled cakes on a platter (or any plate wide enough) and dollop half of the frosting on top. Cover the top and the sides, distributing it equally.
Place the remaining cake upside down on top of the frosted cake and spread the remaining frosting on the top and sides, blending the upper and lower portions of the sides as you go. You may have to evenly shave off any doming on the cake so they lay flush.
The frosting sets at room temperature perfectly. Slice and enjoy!
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Notes
Don't Over-Mix the Batter: this will make the cake turn out too dense because of how the gluten forms. Just mix until the ingredients are combined, and the cake will turn out light and fluffy!Use Room Temperature Ingredients: it’s important that you use room temperature ingredients only. Cold milk will affect the texture of the other ingredients and can affect the final cake.For a Triple Layer Cake: if you want to make 3 8-inch layers, make this recipe, then cut it in half to make the last layer. You may also want to double up on the frosting.Let Cake Cool Before Frosting: frosting the cake too quickly usually results in a crumbly mess. It still tastes fantastic, but it won't look as pretty.Weigh & Scoop the Flour: weighing the flour will ensure that you have the exact amount you need, so that the cake doesn't become too heavy. Scooping the flour into the measuring cup with a spoon will also prevent the cake from becoming too dense, because you won't have packed in any extra flour.