Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.
In a bowl, whisk together flour, baking powder, and salt.
In another bowl, cream butter and sugar until light and fluffy.
Beat in eggs, one at a time, then add vanilla and lemon zest.
Gradually mix in flour mixture, alternating with milk, until smooth.
Fill each cupcake liner halfway with batter and add 1 tsp of raspberry jam in the center.
Cover jam with remaining batter until 2/3 full.
Bake for 18 minutes or until a toothpick comes out clean. Let cool completely.
For frosting, beat butter until creamy, gradually add powdered sugar and lemon juice, and mix until smooth.
Pipe frosting onto cooled cupcakes and drizzle with extra raspberry jam if desired.
