Prepare your pans: use two 7 inch springform pans. Spray/wipe with oil, then dust on a layer of flour. Have two pieces of tin foil ready to go over the pans. Prepare a foil sling. Put 1 1/2 cups water in the bottom of the liner of the IP. Place a small trivet in the liner.
Put the 1 cup of milk into a large glass measuring cup or a small bowl. Add the vinegar and set aside
Mix all the dry ingredients together in a large bowl. Whisk well to combine.
Add the sugar to the milk and whisk well to combine. Make sure the sugar all dissolves. Then, add the oil, and mix very well again.
Pour the wet ingredients over the dry ones and use the whisk to combine well. You want it to just come together, do not over mix.
Pour the batter into the prepared pans, dividing evenly. Cover with foil. Place the sling into the liner of the Instant Pot, just over the trivet and then place both tin foil covered pans stacked into the liner. Lock on lid and make sure toggle is set to sealing.
Manual/high pressure cook the cakes for 35 minutes. Let them have a 10 natural pressure release. Carefully remove the cakes from the IP by lifting them up with the sling. Uncover and allow them to cool completely. Use frosting, whipped cream, or ganache to decorate.