Preheat the oven to 350F & then grease & parchment line 3-7" cake pans
For the cake batter cream the semi soft vegan butter with the granulated sugar on medium high speed for 4-5 minutes until light & fluffy, scraping the bowl several times throughout
Combine the vanilla with the plant milk, then add about ¼ cup of the milk to the creaming butter mixture while mixing on low speed
Sift the dry ingredients together (including the egg replacer) then add 1/3 of that dry mixture to the creaming mixture while mixing on low speed, scrape the bottom & sides of the bowl
Add half of the remaining plant milk, then another 1/3 of the dry.
Repeat with the last of the plant milk & the last of the dry ingredients scraping the bottom & sides of the bowl a few times throughout to make sure there are no lumps. (This entire process of adding the ingredients alternately should not take more than 2 minutes)
Add the pumpkin last, then whip on high for 5 seconds
Divide the batter into your greased & parchment lined cake pans & bake in the preheated 350°F oven for approximately 20-25 minutes or when springy to the touch when you gently press the centers.
Cool completely while you prepare the buttercream recipe as per the instructions on that blog post.
Add the spices and & pumpkin at the last stage of mixing the buttercream
Fill & ice the cooled pumpkin cake layers with the buttercream, decorate as you wish