Goal:

<FruitBasket xmlns="<http://www.fruitauthority.fake>">
  <Fruit>
    <FruitName>Banana</FruitName>
    <FruitColor>Yellow</FruitColor>
  </Fruit>
  <Fruit>
    <FruitName>Apple</FruitName>
    <FruitColor>Red</FruitColor>
  </Fruit>
</FruitBasket>

Code:

XNamespace xns = "<http://www.fruitauthority.fake>";
XDocument xDoc = 
    new XDocument(new XDeclaration("1.0", "utf-8", "yes"),
        new XElement(xns + "FruitBasket",
            new XElement(xns + "Fruit",
                new XElement(xns + "FruitName", "Banana"),
                new XElement(xns + "FruitColor", "Yellow")),
            new XElement(xns + "Fruit",
                new XElement(xns + "FruitName", "Apple"),
                new XElement(xns + "FruitColor", "Red"))
                ));