How to Make It
Preheat oven to 350°F. Coat 10 cavities of 2 (6-cavity) mini fluted tube cake pans (such as Wilton) with baking spray; set aside. Process drained orange pieces, orange juice, and lemon juice in a blender until smooth, about 2 minutes, stopping to scrape down sides as needed. Set aside.
Beat egg whites in a stand mixer fitted with the whisk attachment on high speed until foamy, about 2 minutes. Gradually add 1/2 cup sugar, beating until stiff peaks form, 3 to 5 minutes. Transfer mixture to a large bowl.
Place egg yolks and remaining 1/2 cup plus 2 tablespoons sugar in stand mixer bowl. Beat on high speed until pale yellow and creamy, about 2 minutes. Gently stir egg yolk mixture, orange mixture, and salt into egg white mixture. Gently fold in almond flour.
Spoon batter evenly into the 10 prepared pan molds (about 3/4 cup per mold). Tap pans gently on counter to release any air bubbles.
Bake in preheated oven until cakes are golden brown and edges pull away from sides, 22 to 25 minutes. Let cool in pans 10 minutes. Invert cakes onto a wire rack; let cool completely, about 20 minutes. Serve cakes with almond gelato; drizzle with mostarda liquid, and garnish with chopped toasted almonds.