Spicy Vinegar Chicken over Tomatoes

Name: Spicy Vinegar Chicken over Tomatoes
Cuisine: Mediterranean, Spanish, European
Ingredients: 1 3 ½ - 4 lb. chicken, cut into pieces with the bone-in (or just 3–3 ½ lbs. Bone-in, skin-on chicken pieces, such as legs and thighs, all thighs, etc.); Kosher salt, freshly ground black pepper; 2 tablespoons olive oil, plus more for drizzling; 1 ½ teaspoons crushed red pepper flakes, plus more; ½ cup white distilled vinegar; 1 red or yellow onion, thinly sliced; 4 cloves garlic, crushed; 1 pound tomatoes, thinly sliced