-
1
Preheat the oven to 350F.
-
2
Boil the tangerine-orange juice in a small saucepan over medium-high heat until it has reduced to about 1 cup, 18 to 20 minutes.
-
3
Remove from heat; set aside.
-
4
Pulse cookies, 1 tablespoon lemon zest, and 1/4 cup sugar in a food processor until thoroughly combined.
-
5
With processor running, add melted butter; process until combined.
-
6
Press cookie mixture evenly into bottom, up sides, and onto rim of a 10-inch pie plate.
-
7
Bake until golden brown, about 15 minutes.
-
8
Transfer to a wire rack to cool completely.
-
9
Put lemon juice into a small bowl.
-
10
Sprinkle with gelatin.
-
11
Let soften 10 minutes.
-
12
Meanwhile, whisk together yolks, 1/2 cup sugar, the juice reduction, and the remaining 2 teaspoons zest in a medium saucepan.
-
13
Cook over medium-low heat, stirring constantly, until thickened, about 10 minutes (do not let boil).
-
14
Remove from heat.
-
15
Add gelatin mixture, and whisk until gelatin has dissolved completely.
-
16
Transfer gelatin mixture to a large bowl.
-
17
Refrigerate, stirring occasionally, until cool and thick enough to hold a ribbon on surface, 25 to 30 minutes.
-
18
Put egg whites and cream of tartar into the bowl of an electric mixer fitted with the whisk attachment; beat on medium-high speed until soft peaks form.
-
19
Gradually add remaining 1/4 cup sugar; beat until stiff but not dry peaks form.
-
20
Fold egg-white mixture into gelatin mixture in 3 batches, folding until just combined after each addition.
-
21
Pour into cooled crust.
-
22
Refrigerate until set, at least 2 hours or overnight, before serving.
