Fresh fruit may be used only in small souffles; the short baking time prevents the fruit from becoming too watery.
Heat oven to 400 degrees. Butter dishes well, coat with sugar, and tap out excess. Chill.
Grate peel of 2 of the limes into a small bowl using fine holes of grater. Pour some of the milk into bowl to pick up zest and lime oil. Pour into saucepan along with remaining milk. Scald, turn off heat, cover, and let steep for 15 minutes. Strain.
Using an electric mixer, beat yolks and 1/2 cup sugar until pale and fluffy. Beat in flour until well combined. Slowly add half the hot-milk mixture with mixer running.
Return mixture to saucepan with remaining milk mixture. Bring to a boil over medium-low heat, stirring constantly. Simmer for 2 to 3 minutes more. Transfer to a large bowl and whisk a few minutes to smooth. Grate peel of remaining lime and add to mixture. Cover with plastic wrap, pressing it onto surface. Keep warm.
In a large bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add remaining 2 tablespoons sugar. Beat until stiff and glossy.
Spoon about a third of the whites into lime base and whisk until smooth. Quickly fold remaining whites into mixture until combined. (Don't worry if some streaks remain.) Fill prepared dishes to about 1/4 inch from top. Place a few raspberries in each dish, pressing them gently into batter.Run your thumb around edge of dishes to make a groove.
Place dishes on a cookie sheet. Bake for 10 minutes at 400 degrees, then reduce heatto 375 degrees and bake for another 10 minutes. Dust with confectioners' sugar, if desired,and serve immediately.