Tangelo Crème Brûlée

Preheat oven to 350°F. Finely grate enough zest from tangelos to measure 1 tablespoon. Squeeze enough juice from tangelos to measure 2 cups. In a large bowl gently whisk together whole eggs and egg white until combined well. Add zest, tangelo and lemon juices, and granulated sugar and whisk just until sugar is dissolved. Divide custard among six 1/2-cup ramekins. Put ramekins in a baking pan and add enough hot water to pan to reach halfway up sides of ramekins. Loosely cover pan with foil and bake custards in lower third of oven until just set but still trembling slightly, 20 to 25 minutes. Remove ramekins from pan and cool custards on a rack. Chill custards, loosely covered with plastic wrap, until firm, at least 2 hours, and up to 1 day. Set broiler rack so that tops of custards will be 2 to 3 inches from heat and preheat broiler (or have ready a blow torch). Just before serving, sprinkle 1 teaspoon turbinado sugar evenly over each custard and caramelize under broiler (or with blow torch, moving flame evenly back and forth just over sugar) until sugar is melted and deep golden.