Preheat the oven to 350F and grease two 8″ round cake pans. Line the bottom of each with parchment paper and set aside.

In a measuring glass, combine the milk and vinegar. Set aside.

In a medium bowl, whisk together the gluten free flour, cornstarch, baking soda, baking powder, and salt. Set aside.

In a large mixing bowl using a hand or stand mixer with the paddle attachment, whip together the butter with ¾ cup of granulated sugar. Mix on medium high speed until light and fluffy.

Add in the remaining 1 cup of sugar and oil and mix until smooth.

Now mix in the eggs, two at a time, followed by the vanilla. Mix well to fully combine.

Pour in half of the dry ingredients and mix.

Right before it’s fully combined, mix in the milk and vinegar mixture.

Again, right before it’s fully combined, mix in the remaining dry ingredients to create a smooth batter. It should be pretty thin and pudding-like.

Evenly divide the batter between the two cake pans and spread even.

Bake for 35-40 minutes or until a toothpick in the center comes out clean. They should be golden around the edges and right in the center.

Allow the cakes to cool for about 10 minutes in the pan. Then run a knife along the sides, turn out onto a cooling rack, and peel back the parchment paper.

Completely cool the cakes either at room temp or in the refrigerator before frosting.

In a stand mixer with the paddle attachment, add all of the ingredients for the buttercream. Run on low speed just to combine.

Once everything is smoothed together, crank up the speed to a notch below the highest setting and let it go for 5 minutes.

After 5 minutes, stop and scrape down the bowl. Then crank the speed back up and run for another 5 minutes.

To assemble, spread a layer of buttercream between the two cake layers.

Cover the entire cake in a thin layer of frosting (crumb coat) and chill for 20 minutes.

Once chilled, coat the cake in the remaining frosting. It should be enough to do one thick layer or a thinner layer with enough left to pipe decorations on top.

Finish with some sprinkles and enjoy!