Marinate the liver pieces with lemon juice, vinegar, and spices. Cover and refrigerate for 3 hours.
Heat the butter and oil in a pan over the fire and sauté the liver until browned.
Remove the liver from the pan and place it in an oven-safe dish. Pour the remaining marinade and pan juices over it, cover, and bake in the oven until fully cooked.
Serve the liver alongside the chopped and seasoned vegetables, drizzled with the cooking sauce.