Preheat your oven to 350°F (175°C) and line a standard cupcake pan with paper liners.
In a large mixing bowl, whisk together the plain all-purpose flour, caster sugar, baking powder, and fine salt until well combined.
Carefully divide your batter into two separate bowls. To one bowl, add the strawberry flavoring and a few drops of pink and red food gel. In the other bowl, incorporate the mango flavoring and yellow food gel.
Using a spoon or ice cream scoop, alternately fill the prepared cupcake liners with the two batters, creating a marbled effect.
Bake your cupcakes in the preheated oven for about 18-20 minutes or until a toothpick inserted into the center comes out clean.
Once baked, remove the cupcakes from the oven and let them cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
While the cupcakes cool, prepare your frosting.
Once the cupcakes are cooled, lightly coat the rims with water and roll them in granulated sugar.
Pipe your beautifully colored frosting onto each cupcake using an open star tip, creating appealing swirls.
Top your frosted cupcakes with lime wedges and halved strawberries for a fresh look.