Place trivet in Instant Pot Insert. Put the celery, onions, carrots, and garlic on top of the trivet, and pour in broth.
In a small bowl whisk together melted butter, poultry seasoning, salt, and pepper.
Run the turkey breast under cold water, remove gravy pocket, and pat the turkey breast dry with paper towels.
Use a pastry brush to brush turkey breast with butter mixture. Nestle the turkey breast, breast side up, onto the veggies.
Secure the Instant Pot lid, and make sure that the valve is in the sealing position. Select MANUAL and set the pressure to HIGH and the timer to 35 minutes.
Once the timer goes off, let the pressure release naturally for 25 minutes.
While the pressure releases, move the oven rack to the upper-middle position and preheat the oven to 450 degrees Line a rimmed baking sheet with foil; set aside.
Once the instant pot has naturally released for 25 minutes, move the valve to venting to release any additional steam. Then, open the lid and use a large carving fork to remove the turkey from the Instant Pot.
Place the turkey breast on the prepared baking sheet and roast the turkey in the oven until the skin is crisp and golden in color. DON’T TAKE YOUR EYES OFF THE TURKEY DURING THIS STEP! Remove the breast from the oven and let it sit for 10 minutes before cutting into slices and serving. (While the turkey rests, it’s a good time to make our Instant Pot gravy from the pan drippings!)