Preheat and prepare: Preheat the oven to 425°F (220°C). Pat the chicken thighs very dry with paper towels — removing surface moisture is essential so the skin can brown and crisp rather than steam during cooking.

Season the chicken: Sprinkle 3/4 teaspoon of the kosher salt and half the black pepper evenly over both sides of the thighs. Rub in 1/2 teaspoon of the chopped rosemary and 1/2 teaspoon of the thyme, and gently loosen the skin from the meat with your fingers to push a small amount of the herb mixture under the skin. Putting herbs under the skin flavors the meat directly and helps keep aromatics in contact with the flesh.

Prep the vegetables: Cut the eggplant into 1/2-inch dice, slice the zucchini and yellow squash into 1/3-inch half-moons, dice the tomatoes and bell pepper. Toss the vegetables in a bowl with 1 tablespoon olive oil, the remaining 1/4 teaspoon salt, remaining black pepper, minced garlic, the remaining rosemary and thyme, and optional 1/8 tsp red pepper flakes. Salting the vegetables lightly now helps draw out some moisture so they caramelize rather than stew.

Sear the chicken: Heat a 10–12-inch ovenproof skillet (cast iron is ideal) over medium-high heat until just smoking. Add the remaining 1 tablespoon olive oil and place the thighs skin-side down. Press them briefly with a spatula so the entire skin makes contact. Sear without moving for 4–6 minutes until deep golden-brown — this Maillard browning develops rich flavor and begins to render fat from the skin.

Render and flip: Once the skin is deeply browned, flip the thighs and sear the flesh side for 1–2 minutes just to color. This short sear on the meat side seals flavors and gives a multi-dimensional crust. Remove thighs briefly to a plate.

Build the ratatouille base in the skillet: Reduce the heat to medium. If the pan looks very dry, add a small splash (1–2 teaspoons) of olive oil; pour in the tossed vegetables and spread them into an even layer. Scrape up any fond (browned bits) from searing the chicken — those bits add concentrated flavor to the vegetables. Arrange the thighs on top of the vegetables, skin-side up.

Roast: Transfer the skillet to the preheated oven and roast for 20–25 minutes, or until the internal temperature at the thickest part of the thigh (avoiding bone) reaches 165°F (74°C). Roasting at high heat finishes rendering the skin, cooks the meat through gently, and concentrates the vegetables into a silky sauce.

Rest and finish: Remove the skillet from the oven. Transfer the thighs to a cutting board and let them rest for 5 minutes — resting lets the juices redistribute so they don’t run out when you cut. While the chicken rests, return the skillet to the stovetop over medium heat and simmer the vegetables for 2–3 minutes to reduce any excess liquid and intensify flavor. Taste and adjust seasoning, and squeeze a little lemon or sprinkle lemon zest over the vegetables to brighten the dish.

Serve: Plate a generous spoonful of ratatouille, set a chicken thigh on top, and spoon pan juices over the meat. Garnish with extra thyme or rosemary if desired. The contrast of crisp skin and silky, herb-rich vegetables is what makes this dish sing.