Preheat oven to 350°F (175°C). Line a muffin tin with cupcake liners.
Sift together flour, baking powder, and salt. Set aside.
Cream butter and sugar until light and fluffy. Add eggs one at a time.
Mix in vanilla, then alternate dry ingredients with sour cream.
Fold in lemon juice and zest. Do not overmix.
Prepare filling: Beat cream cheese, sugar, lemon juice, zest, and vanilla until smooth.
Fill liners ⅓ full with batter, add 1 tablespoon cheesecake filling, top with more batter.
Bake 20–22 minutes, until tops spring back lightly when touched.
Cool completely before frosting.
For frosting: Beat cream cheese, butter, powdered sugar, lemon juice, and zest until creamy. Pipe or spread on cooled cupcakes.