Preheat the oven to 350 degrees Fahrenheit. Butter the four cake pans and add parchment paper on the bottom to avoid sticking.
Beat the granulated sugar and vegetable oil in an electric mixer on medium-high speed for about three minutes. The mix should be smooth and creamy.
Beat the eggs in one at a time. Then add the vanilla and beat the mix at high speed for about two minutes. The batter should appear light and fluffy.
In a medium bowl, sift the flour, salt and baking soda. With the mixer on low speed, alternate adding flour mix and buttermilk to the batter. Start with the flour mix and add in three additions, while adding buttermilk after every time.
After about two minutes, the mix should be smooth. Avoid overmixing the batter.
Evenly divide the batter among the four cake pans. Bake two cakes at a time for 15 minutes, or until a toothpick comes out clean. Let the first two cakes cool on a wire rack while the other two are baking.
With an electric mixer, beat the butter and salt on medium speed for about two minutes. Slowly add in the confectioners’ sugar until smooth, then turn the speed to medium-high and beat for two minutes. Gradually add the milk into the frosting until it becomes thick and spreadable in texture.
Once the cakes are completely cool, take a serrated knife to level off the tops of your cakes if they are uneven. This will allow your cakes to be easier to stack and give the finished product a better overall look.
Place one cake layer on a plate, cake stand, or turntable. Using an offset spatula, spread about 1 1/2 cups of frosting on the cake, repeating with each layer. Once all four layers are stacked, use the remaining frosting to cover the sides and top of the cake.