Make the turkey: Place 3 tablespoons unsalted butter in a medium bowl and let sit at room temperature until softened. Prepare the following, adding them to the butter: 1 tablespoon fresh thyme leaves, 1 tablespoon chopped fresh rosemary loaves, 1 tablespoon chopped fresh sage leaves, 1 teaspoon finely grated lemon zest, and 2 minced garlic cloves. Add 1 teaspoon of the kosher salt and 1/2 teaspoon of the ground black pepper, and stir and smash everything together into a paste.
Prepare the following vegetables and place in an Instant Pot or electric pressure cooker: Peel and quarter 1 small yellow onion, peel and cut 1 carrot into 1-inch pieces, and cut 1 celery stalk into 1-inch pieces. Add 1 cup turkey or chicken stock. Top with a heatproof rack.
Pat the turkey breast dry with paper towels. Loosen the skin of the turkey breast. Spread the butter mixture in an even layer under the skin. Season the outside of the turkey breast with the remaining 1 teaspoon kosher salt and 1/2 teaspoon ground black pepper. Place the turkey breast on the rack skin-side up.
Lock the lid on and make sure the valve it set to seal. Set to cook on HIGH pressure for 25 to 30 minutes (5 to 6 minutes per pound of turkey). When the cook time is up, quick release the pressure. Remove the lid and check that the turkey registers at least 165ºF on an instant-read thermometer. If not, cook for 5 minutes more under HIGH pressure, then quick release again.
Arrange a rack in the middle of the oven and heat the broiler. Transfer the turkey breast to a baking sheet skin-side up and pat very dry with paper towels. Broil, rotating halfway through, until golden brown and the skin is crispy, 6 to 8 minutes total. Set aside to rest for 20 to 25 minutes. Meanwhile, make the gravy.
Make the gravy: Pour the turkey cooking liquid (drippings) through a fine-mesh strainer into a bowl. Discard the contents of the strainer. Using a fat separator or skimming with a spoon, remove the fat from the drippings and discard. Measure out 2 1/4 cups of the remaining drippings (save the rest for another use).
Wipe out the bowl of the Instant Pot, add 4 tablespoons unsalted butter, and melt on the Sauté function. Whisk in 1/4 cup flour and cook for 2 to 3 minutes. While whisking continuously, slowly pour in the drippings, and simmer until the gravy is thickened, about 3 minutes. Turn off the cooker. Taste and season with more salt and pepper as needed. Carve the turkey and serve with the gravy.
