Place rack in upper third of oven and preheat to 400 degrees.
Wash chicken inside and out with cold water, remove the giblets, then let the chicken drain, cavity down, in a colander until it reaches room temperature (about 15 min) Pat dry with paper towels.
Pour lemon juice all over the chicken (inside and outside) season with salt and pepper.
Prick the whole lemons three times with a fork and place deep inside the cavity.
(Tip: If lemons are hard, roll on the countertop with your palm to get juices flowing.) Place the chicken breast-side down on a rack in a roasting pan, lower heat to 350 and bake uncovered for 15 minutes.
Remove from oven and turn it breast-side up (use wooden spoons!); return it to oven for 35 minutes more.
Test for doneness - a meat thermometer inserted in the thigh should read 180, or juices should run clear when chicken is pricked with a fork.
Continue baking if necessary.
Let chicken cool for a few minutes before carving.
Serve with juices.
Serve with boiled new potatoes tossed with olive oil and fresh chopped parsley and/or steamed asparagus with butter.