In a medium bowl, add the flour, baking powder, baking soda, cinnamon, and salt. Set that aside.
In a large bowl, add the melted butter, granulated sugar, and brown sugar. With a whisk, mix well until fully combined. Add the eggs one at a time and mix well after each egg.
Add the shredded carrots, crushed pineapple, and walnuts to the batter. Mix well.
Add the flour mixture to the large bowl. Mix until fully combined and there the flour is fully combined.
Butter the springform pan well and pour the batter into the springform pan. Cover tightly with aluminum foil.
Add 1 cup of water to your Instant Pot. Place the springform pan on the trivet insert. Add the trivet insert and pan into the Instant Pot. Cover the Instant Pot, make sure it is set to "sealing" and set the Instant Pot to "steam" for 45 minutes.
Allow the Instant Pot to naturally release for 10 minutes. Carefully lift out the cake and place it on a wire rack. Make the cream cheese frosting while the cake cools for at least 30 minutes.
Once the cake has cooled for at least 30 minutes, remove from the springform pan and ice the cake to your liking.