Preheat the oven to 350°F. Using a stand mixer with a paddle attachment, cream together the sugar, sour cream, vegetable oil, butter, lemon juice, vanilla, and egg.
In a separate bowl, whisk together the flour, baking soda, and salt. Slowly sift the flour mixture into the creamed mixture. The batter should be thick but still runny.
Fill muffin tins lined with papers about 2/3 of the way full. Bake in the oven for 25-30 minutes or until the tops are golden brown and just beginning to crack. A toothpick inserted in the center should come out clean.
Cool the cupcakes completely.
Use a food processor to blend the strawberries. Optional step: strain the strawberries through a cheesecloth to remove seeds.
Stir the strawberry puree into the powdered sugar along with the butter and lemon juice until a thick frosting forms. The frosting should stand on its own when a spoon is inserted into the frosting and then removed.
Use a piping bag or spoon to cover the tops of each cupcake with frosting. If using a piping bag, start in the center of the cupcake, then swirl out and overlap upwards.
Serve cupcakes with mini straws and a tall glass of ice-cold pink lemonade. Enjoy!