If you don't have a steamer, use a large pot with your colander as your steamer basket, but don't forget to put the lid back on! The lid does not need to fit tightly for the artichokes to still cook.
More sugar may be needed depending on acidity of tomato, but only add 1 pinch at a time.
Dip can also be made ahead of time. Tightly covered, it will keep for about 1 week in the refrigerator.