In a heat-safe glass bowl, small enough to fit in your instant pot, add the blueberries, 2 Tablespoons of melted butter, cinnamon, cornstarch, and sugar. Toss to coat the berries.
Add just enough cake mix to cover all the berries. I used about 1 ½ cups.
Cut the remaining 4 Tablespoons of butter into small pats and place all over the top of the cake mix.
Cover the top of the bowl tightly with aluminum foil.
Add 1 cup of water to the bottom of the Instant Pot and place the trivet inside. Place the bowl on top of the trivet
Make sure the lid is sealed and set the Instant Pot on high pressure for 13 minutes. Allow to naturally release for 5 minutes.
Remove the bowl from the pot and remove the aluminum foil and place under a broiler for 3-4 minutes or until the top is a nice golden brown.
Allow to cool for 5 minutes then serve with vanilla ice cream.