Step 1

Arrange a rack in the middle of the oven and heat the oven to 400ºF. Halve 1 medium yellow onion, then cut into 1-inch thick wedges.

Step 2

Season 4 bone-in, skin-on chicken thighs with 1 teaspoon kosher salt. Place skin-side down in an unheated large cast iron skillet. Place over medium-high heat and sear undisturbed until the chicken skin is golden brown and releases easily from the pan, about 10 minutes.

Step 3

Flip the chicken and sear until browned on the second side, about 5 minutes. Meanwhile, place 1/2 cup mayonnaise in a small bowl, add 1 envelope onion soup mix, and stir to combine.

Step 4

Transfer the chicken to a plate. Add the onion wedges to the pan and cook, trying to keep them intact as much as possible, until light golden brown on both sides, about 2 1/2 minutes per side.

Step 5

Add 2 tablespoons of the apple cider vinegar and 1 teaspoon chicken bouillon paste and scrape up any browned bits from the bottom of the pan with a wooden spoon. Turn off the heat.

Step 6

Dollop 1 tablespoon of the mayonnaise mixture onto each piece of chicken and spread all over with the back of a spoon. Return the chicken skin-side up to the pan, moving the onions around as needed so they aren’t covered by the chicken.

Step 7

Transfer the pan to the oven and roast until the internal temperature of the thickest part of the chicken not touching bone registers at least 165ºF on an instant-read thermometer, about 20 minutes. Meanwhile, finely chop 1 medium bunch fresh chives until you have 3 tablespoons. Add 2 tablespoons of the chives and 1/2 cup Greek yogurt to the remaining mayonnaise mixture and stir to combine.

Step 8

When the chicken is ready, if you’d like a bit more color and crunch, turn the oven to broil and broil until well browned and the skin is crisp, about 2 minutes.

Step 9

Transfer the chicken to a plate. Add the remaining 1 tablespoon apple cider vinegar and 1/2 teaspoon black pepper to the pan and scrape up the browned bits from the bottom with the wooden spoon.

Step 10

Spread the yogurt mixture onto a large plate. Top the yogurt mixture with the onions and chicken. Pour the drippings in the pan over the chicken. Sprinkle with the remaining 1 tablespoon chives.