Grease all sides of the cake pan.
Add 1 cup of water to the Instant Pot insert.
Beat cake mix, 1 cup water, 1/3 cup oil and 3 whole eggs in a bowl.
Pour the batter in the greased cake pan.
Gently cover the cake pan with a paper towel.
Using a piece of aluminum foil, cover the paper towel and gently secure the paper towel around the rim of the pan.
Place the cake pan on the trivet and carefully place the trivet inside the Instant Pot.
Press the “Cake” button and set the mode to “Less”. Adjust the cook time to 50 minutes.
Allow Natural Pressure Release.
Start the glaze whisk together the powdered sugar and milk until you reach your desired consistency.
Zest an orange and mix again.
Pour glaze over top the cake, set aside until glaze hardens.
Cut and enjoy!