Prepare lemon curd ahead, as directed. Keep chilled until ready to use.
Preheat oven to 350°F. Line a cupcake pan with 8 paper liners.
In a large bowl or stand mixer, cream together butter and sugar until light and fluffy. Mix in egg, lemon zest, lemon juice, and vanilla extract until smooth. Scrape the bowl as needed. Add salt and baking powder, mixing until just combined. Alternate additions of flour and sour cream until fully combined and no streaks remain.
Divide batter between prepared baking cups, filling roughly 2/3 full. Bake for 18-20 minutes or until a toothpick inserted comes out clean. Cool in pan until easy to handle, then transfer to a wire rack to cool completely.
For frosting, in a large bowl or stand mixer, beat together butter, vanilla, strawberry jam, and strawberry extract until fully combined. Gradually add powdered sugar, mixing until smooth. Add red gel food color for a brighter shade of pink if desired.
Use a sharp knife or cupcake corer to remove the center of each cupcake. Fill with lemon curd and replace the top of the core. Frost cupcakes with prepared frosting and top each with a fresh strawberry.