Preheat oven to 350°F (176°C) and lightly grease the cake pan
Mix the lemon juice and plant milk until combined and let sit for 10 minutes. This is your vegan buttermilk.
In a large mixing bowl, whisk the 2 ½ cups cake flour, 1 tablespoon + 1 teaspoon cocoa powder, 1 teaspoon baking soda, and ½ teaspoon salt until completely combined.
In a medium mixing bowl, whisk the ¾ cup canola oil, 1 cup buttermilk, 1 ½ cups sugar, 1 tablespoon vanilla, egg replacer, 2 teaspoon apple cider vinegar, and 3 tablespoon red dye until combined. Add beet root powder by the tablespoon until it turns a nice red color if you don’t use the food dye.
Pour the wet oil mixture into the dry mixture and beat with a paddle attachment until just combined. Slowly add the boiling water until combined. The batter will be thin, not thick.
Fill each skull mold until almost full. Bake for approximately 45 minutes, or until a wooden toothpick comes out clean when inserted in the center.
Cool in the pan for 10 minutes and then invert onto a cooling rack until they’re completely cool.
While the cakes are cooling, make the glaze.
When the cakes are completely cool, drizzle the glaze over the tops of the cakes so it pools int the eye and nose sockets and drips down the sides.
FOR THE ICING
In a small bowl, stir 1 tablespoon into the sugar until the sugar starts to form a glaze, add more milk as needed until it’s the consistency you’re looking for to drizzle over the cakes.
If you add too much milk, add a small amount of sugar too thicken.