Celebrate citrus season with individual dessert souffles made with tangerine juice and zest. Dust them with confectioners' sugar, and offer creme fraiche alongside.
Preheat oven to 400 degrees with rack in lower third. Butter six 6-ounce ramekins; coat with superfine sugar. Place on a rimmed baking sheet.
Bring milk, vanilla bean and seeds, and salt to a simmer in a medium saucepan over medium-low. In a large bowl, whisk together yolks and 1/4 cup superfine sugar until pale and fluffy, 1 to 2 minutes. Add flour and whisk until well combined.
Remove vanilla bean from milk mixture (discard or reserve for another use), then gradually add half to yolk mixture, whisking constantly. Whisk yolk mixture into remaining milk mixture in saucepan. Bring just to a boil, whisking constantly, then reduce heat and simmer until thick and smooth, 1 to 2 minutes. Remove from heat; whisk in zest and juice. Transfer to a large bowl and cover with plastic wrap, pressing it directly onto surface of mixture. Let cool completely.
In another bowl, whisk egg whites and cream of tartar until soft peaks form. Gradually add remaining 2 tablespoons superfine sugar and whisk until peaks are stiff and glossy, 1 to 2 minutes.
Spoon one-quarter of whites mixture into custard base, then whisk thoroughly until smooth. Gently fold in remaining whites mixture until combined. (Don't worry if some streaks remain.) Divide evenly among prepared ramekins. Bake until risen and set, 15 to 16 minutes. Serve immediately, dusted with confectioners' sugar and with creme fraiche alongside.