Step 1: Marinate the Chicken

Begin by patting the chicken thighs dry and placing them in a large bowl. Season generously with kosher salt and freshly ground black pepper. Add the minced garlic, chopped rosemary, red-pepper flakes, lemon zest, and lemon juice. Drizzle with one tablespoon of olive oil and toss the thighs to coat evenly. Allow the chicken to marinate at room temperature for at least one hour, or for best results, refrigerate overnight.

Step 2: Prepare the Peppers

In a large skillet, heat two tablespoons of olive oil over medium-high heat. Once the oil shimmers, add the sliced onions and cook, stirring frequently, until they soften but do not brown. Next, add the bell peppers, stirring to combine. Season with salt and pepper, then add the grated garlic and red-pepper flakes. Reduce the heat to medium, partially covering the skillet with a lid, leaving a small gap. Allow the peppers and onions to cook for approximately 15 minutes, stirring occasionally, until fully softened.

Step 3: Final Touches on the Peppers

Add the green and black olives, red wine vinegar, and capers to the skillet, continuing to cook for a few minutes to allow the flavors to meld. Taste and adjust the seasoning as necessary, then sprinkle with dried oregano. Set the mixture aside to serve either warm or at room temperature.

Step 4: Cook the Chicken

Heat a large cast-iron skillet or heavy-bottomed pan over high heat. Add the remaining three tablespoons of olive oil. When the oil begins to shimmer, place the chicken thighs, skin-side down, into the pan. Gently shake the pan to ensure the chicken does not stick.

Step 5: Crisp the Skin

Reduce the heat to medium and cover the chicken with a piece of parchment or aluminum foil. Place another skillet on top of the chicken and weigh it down with a heavy object, such as a brick or canned goods. Lower the heat to low and cook for about 20 minutes, occasionally checking to ensure the chicken is not sticking. The skin should become beautifully browned and crisp during this time.

Step 6: Cook the Chicken Through

Flip the thighs over and cook for an additional 10 minutes, or until the chicken reaches an internal temperature of 165°F and the juices run clear. If desired, return the chicken to skin-side down and cook for a few more minutes to further crisp the skin.

Step 7: Serve

Place one chicken thigh on each plate, accompanied by a generous spoonful of the pepper, olive, and caper mixture. Leftover peppers can be stored in an airtight container in the refrigerator for up to one week.