Start by heating a large Dutch oven over medium-high heat. If you don’t have a Dutch oven, a cast iron skillet works just as well.
In a small bowl, combine the kosher salt, black pepper, granulated onion, granulated garlic, lemon pepper, chili powder, and cayenne pepper.
Rub the seasoning mixture all over the boneless, skinless chicken thighs, ensuring they're well-coated on all sides.
Add the neutral oil to the preheated Dutch oven. Place the chicken thighs in the pot and brown them on both sides, about 6 minutes total. Once browned, remove the chicken and set it aside.
In the same Dutch oven, add the unsalted butter and sliced onions. Stir with a wooden spoon or spatula, scraping up any browned bits from the bottom. Sauté the onions until they're soft and translucent, about 5 to 7 minutes.
Gradually sprinkle in the flour and chicken bouillon powder, stirring continuously until the mixture is well-blended with the onions and butter. Slowly add the chicken stock, whisking vigorously to create a smooth gravy. Taste and adjust seasoning if necessary.
Return the browned chicken thighs to the Dutch oven, nestling them into the gravy. Bring the gravy to a low boil, then reduce the heat to low. Cover the pot and simmer the chicken in the gravy for 25-30 minutes, stirring occasionally, until the chicken is tender and cooked through.
Plate the smothered chicken with a generous scoop of cooked white rice and ladle extra gravy on top. Serve immediately and enjoy!