pre-heat oven to 450 ℉ - do not submerge your chicken into the tomato sauce, nestle them in keeping the skin out of the liquid. they will get even more crispier and browner in the oven
Pat the chicken dry and In a small bowl, stir 2 teaspoons of coriander, 1 teaspoon salt and ½ teaspoon black pepper together and sprinkle it all over both sides of the chicken
In an oven safe skillet, heat over medium heat, add the oil until shimmering. add the chicken skin side down. cook until well browned, about 6 minutes or so. Transfer the chicken to a plate, pour off and discard all but a couple of tablespoon of the oil.
With skillet over medium heat add the onions, stirring occasionally, until they begin to soften, about 5 minutes. Add the remaining coriander, garlic, red pepper flakes and a ½ teaspoon kosher salt. cooking till fragrant about 30 seconds or so. Add the tomatoes and cook, scraping up any browned bits, about 4-5 minutes or until the tomatoes begin to release their juices.
Nestle the chicken skin side up into the tomato mixture, do not submerge the skin. Add any juices collected on the chicken plate. Transfer to the preheated oven and cook for about 20-25 minutes. Or until the thickest part of the thigh reaches 175℉. Remove from the oven and serve with the herbs sprinkled all over.