Mix eggs, egg yolks, tangerine juice, and 1/4 cup sugar in a medium bowl until blended. In a medium saucepan, heat cream and zest over medium-low heat, stirring occasionally, until just about to boil. Remove from heat and let steep for 30 minutes. Reheat cream until almost boiling again. Add hot cream to the egg mixture a ladleful at a time, stirring constantly.
Add salt and vanilla to hot custard mixture and stir to combine. Pour custard through a fine-mesh strainer into a bowl or measuring cup with a pouring spout.
Preheat oven to 350°. Put 8 ramekins (6 oz. each) in a roasting pan and divide custard among ramekins (about 1/2 cup per ramekin). Add enough boiling water to come about three-quarters up the sides of ramekins. Cover pan with foil.
Bake custards until just set, about 20 minutes (start checking early). Remove custards from water bath with tongs and let cool about 20 minutes. Chill custards at least 4 hours.
Sprinkle 2 tsp. sugar evenly over each custard. Use a kitchen blowtorch to melt and set the topping*. Serve immediately.
Make ahead: Up to 4 days through step 4, covered with plastic wrap.
*For even browning, rotate custard while flaming. If you have a gas broiler, the custard tops can be broiled, as close to the heating element as possible without touching, but the results will not be as consistent as with a blowtorch. Kitchen torches (from $30) are available online and at cooking-supply stores.
Note: Nutritional analysis is per serving.