What is the best way to return two lists in C#?

I am almost embarrassed to ask this question, but as a long time C programmer I feel that perhaps I am not aware of the best way to do this in C#.

I have a member function that I need to return two lists of a custom type (List<MyType>) and I know beforehand that I will always have a return value of only two of these lists.

The obvious options are :

public List<List<MyType>> ReturnTwoLists();

or

public void ReturnTwoLists(ref List<MyType> listOne, ref List<myType> listTwo);

Both seem to be non-optimal.

Any suggestions on how to improve this?

The first way doesn't make it clear in the syntax that only 2 lists are being returned, and the second uses references rather then a return value, which seem so non-c#.