Rinse and dry the outside skin of the acorn squash.
Cut the acorn squash in half. See notes in the blog post and in the notes below for tips regarding cutting the squash.
Scoop out the seeds in the middle using a spoon or an ice cream scoop and discard the seeds (or you can save the seeds to roast later.)
Place the inner liner into the Instant Pot.
Pour 1 cup water into the inner liner.
Place the 2 acorn squash halves on the trivet that came with the Instant Pot with the cut side facing up.
In the center of each acorn squash half, place 1 Tablespoon butter, 1 Tablespoon brown sugar, and sprinkle 1 teaspoon of cinnamon over the top of the butter and brown sugar.
Close the lid of the Instant Pot. Move the pressure release valve to the "SEALING" position.
Press "PRESSURE COOK" or press "MANUAL" on the front of the Instant Pot. Press + or - to adjust the time to 7 minutes. (NOTE: It will take several minutes for the Instant Pot to come up to pressure.)
When the Instant Pot has finished cooking, let the pressure release naturally for 10 minutes (which means you do nothing for 10 minutes), then after 10 minutes, do a QUICK RELEASE by moving the pressure release valve to the VENTING position.
After the pressure has been fully released and the pin on top has dropped, carefully remove the lid. Then carefully remove each half of the acorn squash, one by one and move to a serving plate or dinner plate. Enjoy!