In a small heavy-bottomed pot, combine
whole eggs, 1 cup of the sugar, the Key
lime juice and butter over medium heat.
Cook, stirring constantly, until mixture
reaches 175° and coats the back of a
spoon, about 8 minutes. Be careful not
to heat mixture above that temperature
or it will curdle. Pour into a bowl
through a mesh strainer. Cool completely,
cover with plastic wrap and refrigerate
Heat oven to 375°. Beat 1 of the egg
whites. Place pie shells on a baking sheet
and brush with egg white. Bake at 375° for
5 to 7 minutes or until golden-brown.
Cool completely on a baking rack.
Fill cooled piecrusts with cooled lime
curd. Cover gently with plastic wrap and
refrigerate for 2 hours.
Heat broiler to HIGH. With a hand
mixer or a stand mixer fitted with
whisk attachment, combine remaining
3 egg whites and the cream of tartar.
Beat on high until soft peaks form. With
machine running, pour in remaining
3 tbsp sugar and beat on high until stiff
peaks form. Do not over-beat. Spoon
meringue onto pies, using back of spoon
to create texture. (Alternately, pipe
meringue in a continuous spiral around
curd.) Broil on HIGH for 30 seconds to
1 minute, about 7 inches from the top,
until meringue is golden.