Here is a basic tutorial. I used 1 yard flowy fabric. Hem sides and bottom. Measure how long from child's shoulders. I just eyed it up *wink*
Then sew large stitches across the top and pull one of the threads to "gather" around neck. I again measured this on my actual child to see how wide I needed it to be and adjusted by pulling- easy!
Then I added a layer of pink tulle and a grosgrain ribbon for ties. Pin ribbon over gather stitches, hiding tulle edge. (I sewed tulle up over edge of cape and went back after sewing and trimmed it off.)