Caramelized Lemon Tart

Place sugar and lemon in a large stainless-steel bowl. Push yolks through a sieve into bowl, and whisk to combine.

Set bowl over a pot of simmering water, and stir slowly until mixture thickens, 15 to 20 minutes. Cook 5 minutes longer.

Remove bowl from heat, and stir in zest. Stir in butter piece by piece until completely melted. Pour into cooled tart shell. Chill until firm, at least 1 hour.

Preheat broiler. Remove outer ring from tart pan, and place pan on a large cookie sheet. Place outer ring upside down on top to protect pastry from burning.

Sift sugar evenly over top, and place under broiler. Watch carefully; remove tart when top is evenly browned.