Remove the turkey breast from packaging and make sure to remove anything from inside the turkey cavity. Pat dry with a paper towel.
In a small bowl, mix together the softened butter (4 tablespoons), kosher salt (1 tablespoon), black pepper (1 teaspoon), lemon zest, and fresh thyme leaves (2 tablespoons).
In the bottom of your pressure cooker, place the onion, celery, and carrots. Add the lemon halves leftover from zesting, and the springs from which the thyme leaves have been removed as well.
Pour in the chicken broth (1 cup) on top and place the wire trivet that came with your instant pot inside.
Rub the butter mixture all over the turkey, including under the skin, being careful not to tear the skin (but if you do, don't worry! It will be fine.).
Place the turkey in the pressure cooker on top of the wire trivet, making sure it's in all the way. Smush it down if you need to.
Place the cover on and in the locked position, and double check that the pressure release valve is in the "sealed" position.
Set your pressure cooker to manual high pressure for 35 minutes.
Once it's done, allow the pressure to naturally release for 10 minutes. Then, you can quick release the pressure and remove the turkey carefully once the float valve has depressed, indicating the pressure has fully released.
If you want crispy skin, place the turkey on a wire rack nestled into a baking sheet and broil it for 5-10 minutes, until you've reached the desired color and crispiness.
Allow the turkey to rest, uncovered, for at least 20 minutes before carving into it, so the juices can redistribute.
Carve, slice, and serve!
The cooking time indicated does not include the time it takes your pressure cooker/Instant Pot to come up to pressure and release the pressure. Plan for about an hour total cooking time, accounting for the pressure rise and release.
The drippings from the bottom of the instant pot after cooking can be used to make turkey gravy.
To make this in your slow cooker, place the veggies in the bottom of a large crockpot along with the broth, and the buttered turkey breast on top. Cook on low for 6 hours, or until internal temp is 165 degrees F.
You can freeze the leftovers sealed tightly in a plastic bag with as much air squeezed out as possible.
I made this recipe in my 6 qt. Instant pot. It should work the same in an 8 qt., but you may need to cut the ingredients in half for a 3 qt. mini, and a whole turkey breast likely won't fit in a mini.
The provided nutrition information is my best estimate. It does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.