Preheat the oven to 350°F. Line a cupcake pan with 12 paper liners.
Combine the strawberries, soda, and 1 tablespoon sugar in a small saucepan and cook over medium heat. Stir well until the liquid is mostly absorbed and the mixture is syrupy. This will take about 7-10 minutes. Set aside to let cool.
In the bowl of an electric mixer, beat the butter until creamy. Add the remaining 3/4 cup sugar and beat again until fluffy. Beat in the eggs one at a time. Pour in the cooled strawberry mixture and beat on low speed until combined.
In a separate small bowl, mash the banana with the lemon juice. Add it to the creamed butter mixture and beat until incorporated.
In a separate large bowl, combine the cake flour, baking soda, baking powder and salt. Whisk to combine. Add the flour mixture to the creamed mixture alternately with the buttermilk on low speed. Add the food color, if using.
Fill each cupcake paper 3/4 full and bake for 16-20 minutes, or until a toothpick tester comes out clean. Let the cupcakes cool in the pan 5 minutes before removing them to a wire rack. Cool completely.
For the strawberry buttercream, combine the strawberries and lemon-lime soda in a small saucepan and cook over medium heat. Stir well until the liquid is mostly absorbed and the mixture is syrupy. This will usually take about 7-10 minutes. Mash cooked strawberries with a fork or puree in a blender. Set aside to let cool completely.
In the bowl of a standing mixer fitted with the whip attachment, beat the butter until creamy. Add the powdered sugar and mix until crumbly. Pour in the cooked strawberry puree and mix well. Add milk or cream 1 tablespoon at a time to thin the mixture to piping consistency (I only needed 1 1/2 tablespoons). Add food color, if using.
Transfer frosting to a piping bag fitted with a plain 1/2-inch round tip. Pipe frosting onto cooled cupcakes. Generously garnish with sprinkles.
Cake recipe adapted from “Intoxicated Cupcakes” by Kate Legere