My pattern says rib 3, cast off next 2 sts, rib to end. Next row - rib to end casting on 2 sts over cast off sts. My problem is, this is 1 x 1 ribbing so casting off two stitches will include both a knit stitch and a purl and casting on using cable cast on is confusing and looks messy. I usually use eyelet buttonholes over the purl stitches but this would be rather small for the button. Could you please advise. Thank you.

Are you using the cable cast on to simply cast on knit sts or are you trying to cast on knit and purl sts? It’s better to cast on as knit sts and on the next row, incorporate those sts into the 1x1 rib. I find that the buttonhole recedes into the rib after a few rows.

This video also uses cable cast on for a one row buttonhole which is a neat technique to use. The demo is over stotckinette but it works well with rib too.

Thanks for this. I got there eventually when I discovered the written version. It seems however, that it’s a tight buttonhole and three stitches cast off, would be better than the two my pattern suggests in order to accommodate the size button intended for the garment.