Preheat the oven to 350°F.
Lightly oil and line the bottoms of two round 9-inch cake pans* with parchment paper.
In a small bowl or liquid measuring cup, stir together the milk, coconut oil, vanilla, and vinegar.
In a large mixing bowl, stir together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Use a spoon to make a well in the center of the flour mixture, then pour the milk mixture into the well.
Beat the ingredients together using an electric mixer at high-speed, scraping down the sides of the bowl as needed. Beat until the ingredients are completely mixed, about 2 minutes.
Divide the batter among the two prepared cake pans.
Bake for about 25 minutes, until a toothpick inserted into the center of each layer comes out clean.
Remove the cake pans from the oven and transfer them to a cooling rack. Allow the cakes to cool completely.
To frost the cake, invert one of the layers onto a plate, then peel off the parchment paper.
Smooth a layer of frosting over the top of the cake.
Invert the second layer over the first layer and remove the parchment paper.
Slather a layer of frosting over the second cake layer.
Cover the sides of the cake with another thin layer of frosting.
Cut the cake and serve immediately or chill for later.