How to Make It
To prepare the lime filling, combine 1 teaspoon lime rind, 1/4 cup lime juice, and sweetened condensed milk in a small bowl, stirring until blended. Cover and chill 3 hours.
Preheat oven to 325°.
To prepare cake, coat bottoms of 3 (8-inch) round cake pans with cooking spray (do not coat sides of pans); line bottoms with wax paper. Coat wax paper with cooking spray; dust with 1 tablespoon flour.
Lightly spoon 2 cups cake flour into dry measuring cups, and level with a knife. Combine 2 cups cake flour, 1 cup sugar, baking powder, and 1/2 teaspoon salt in a large bowl, stirring with a whisk until well combined.
Combine oil, 1/3 cup juice, 3 tablespoons water, 1 teaspoon rind, lemon extract, and egg yolks in a medium bowl, stirring with a whisk. Add oil mixture to flour mixture; beat with a mixer at medium speed until smooth.
Place egg whites in a large bowl; beat with a mixer at high speed until foamy. Add cream of tartar; beat until soft peaks form. Gradually add remaining 1/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently stir one-fourth of egg white mixture into flour mixture; gently fold in remaining egg white mixture.
Divide cake batter equally among prepared pans, spreading evenly. Break air pockets by cutting through batter with a knife. Bake at 325° for 20 minutes or until cake springs back when lightly touched. Cool in pans for 10 minutes on a wire rack; remove from pans. Remove wax paper from cake layers. Cool completely on wire rack.
To prepare frosting, combine 3 tablespoons sugar and 2 tablespoons lime juice in a small glass bowl. Microwave at high for 30 seconds or until sugar dissolves. Cool completely. Fold into whipped topping.
To assemble cake, place 1 cake layer on a plate; spread half of filling over cake layer. Top with second layer, remaining half of filling, and third layer. Spread frosting over top and sides of cake. Garnish with mint, blueberries, and lime wedges, if desired. Store cake loosely covered in refrigerator for up to 3 days. Slice cake into wedges.