Squeeze lemon juice into a large bowl of water. To prevent browning, dip the artichokes into the lemon water as you work, and reserve the prepared artichokes in the lemon water.
To prepare the artichokes peel away and discard the tough outer leaves until you reach the light green tender leaves. Cut off the tough top part of the leaves. At the bottom, trim the stem leaving 1 to 2 inches; pare away all rough dark green parts of the remaining stem and the bottom of the artichoke. Chop the artichoke in half lengthwise or into 4 wedges. If necessary remove the choke and any shiny, pointy center leaves and then slice as thinly as possible lengthwise. Reserve the prepared artichokes in the lemon water.
To serve, drain well, toss with lemon juice, olive oil salt and pepper, top with shaved parmigiano to serve.