Preheat the oven to 200°C/400°F.
Clean chicken with a vinegar-water rinse and trim excess fat. Combine seasonings with olive oil and rub all over chicken, including under the skin. Let rest for 5 minutes.
Heat a skillet over medium heat with oil. Sear chicken skin-side down until golden, flip, and sear the other side. Transfer to a wire rack or baking dish and roast until cooked through, about 20 minutes.
Heat olive oil in a saucepan and sauté onions until translucent. Stir in rice, water, and salt. Cover and cook until tender, 15 minutes.
Melt butter and whisk in lemon zest, lemon juice, and lemon pepper. Drizzle over chicken before serving.