Grab a large mixing bowl, mix cake mix, eggs, water, and oil together until well blended.
Next, mix in the blackberries. Or another berry if you like.
Give the 7-inch bundt pan a good greasing then lightly dust with flour.
Now pour the mixed cake batter into the bundt pan.
Pour 1 cup of water to the inner pot of the Instant Pot. Then place the trivet inside the pot.
Make a foil sling (or use a bought one) and carefully lower filled bundt pan into the pot onto the trivet. Loosely fold foil sling over the top of the bundt pan.
Next, close the lid and turn the valve to sealing.
Cook on high pressure for 35 minutes.
When it is done, open the valve for quick pressure release.
When pressure is gone, open the lid and carefully lift the sling out of the pot. Let cool on the counter for 30-60 minutes.
Use a plastic knife (or another flat object) to gently separate the cake from the sides pan. Then place a wire rack on top of the pan and flip it over to empty the cake onto the rack.