1/2 teaspoon gelatin
2 tablespoons Meyer lemon juice
1 cup juice and 3 tablespoons grated zest from 3 blood oranges
1/2 cup sugar
4 egg whites whipped to stiff peaks
1 cup cream whipped to stiff peaks
1 pound frozen sweetened blackberries, thawed, pureed, strained
Dissolve gelatin in 2 tablespoons cold water. Warm lemon juice, orange juice and sugar over low heat until sugar dissolves, about 1 minute. Stir occasionally until mixture cools and thickens slightly.
Fold whipped egg whites into orange-lemon mixture, then fold in whipped cream. Pour into 6 8-ounce custard cups . Chill until set, about 3 hours or overnight.
Unmold blood orange snow on to chilled plates. Drizzle blackberry puree over each dessert; serve immediately.