Halve the lemon. Squeeze the juice from half the lemon into a medium bowl and fill the bowl halfway with cold water. Trim the artichokes as described. Cut them into wedges about ½ inch thick and put them in the bowl of lemon water to prevent them from discoloring.
Peel and finely chop the onion and garlic. Finely chop enough of the parsley leaves to measure 1tablespoon. Put the olive oil and onion in a medium braising pan over medium heat. Sauté, stirring occasionally, until the onion turns a rich golden color, about 5 minutes.
Add the garlic and parsley and stir for about 20 seconds. Drain the artichokes and add them to the pan along with ¼cup water. Season with salt and pepper and cover the pan. Cook until the artichokes are tender, about 20 minutes. If all the water evaporates before the artichokes are done, add alittle more water, a couple tablespoons at a time.
When the artichokes are tender, uncover the pan and simmer until any remaining water evaporates. Serve at once.
The artichokes can be prepared several hours ahead of time and kept in the pan. Once refrigerated, they will not taste as fresh.