Transpose list of lists

Suppose I have

l = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

How can I get a result like so?

r = [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

I know how to get

r = [(1, 4, 7), (2, 5, 8), (3, 6, 9)]

but I must have lists as elements of the result.