In a saucepan, combine white vinegar, water, sugar, and salt. Bring to a boil, then add sliced Fresno chilis. Remove from heat, let cool, and refrigerate for at least 1 hour.

Caramelize the Onions

In a skillet, heat olive oil over medium heat. Add sliced onions and salt, cooking slowly until they are golden brown and caramelized, about 20-25 minutes.

Make the Chimichurri

In a food processor, combine parsley, olive oil, red wine vinegar, garlic, and red pepper flakes. Blend until smooth and well combined.

Cooking the Chicken and Potatoes

Prepare the Chicken

Preheat your oven to 450°F (230°C). Season the whole chicken inside and out with salt and black pepper. Heat olive oil in a large oven-safe skillet over medium-high heat.

Sear the Chicken

Place the chicken breast-side down in the skillet and press down with a heavy object (like a brick wrapped in foil) to ensure even cooking. Sear for about 10 minutes until the skin is crispy and golden.

Roast the Chicken

Turn the chicken over, transfer the skillet to the preheated oven, and roast for an additional 25-30 minutes until the internal temperature reaches 165°F (75°C).

Cook the Potatoes

Meanwhile, boil the Yukon Gold potatoes in salted water until fork-tender. Drain and toss with butter and salt.