Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners. In a medium bowl, whisk together the sifted flour, baking powder, baking soda, and salt. In a large bowl, cream the softened butter and granulated sugar until light and fluffy, about 3 minutes. Beat in eggs one at a time, then mix in vanilla, lemon zest, and lemon juice.

With the mixer on low, add half of the dry ingredients to the butter mixture, then all of the buttermilk, then the remaining dry ingredients. Mix until just combined; do not overmix.

Divide the batter evenly among the 12 cupcake liners, filling each about 2/3 full. Drop a teaspoon of raspberry jam onto the center of each cupcake. Use a toothpick or skewer to gently swirl the jam into the batter.

Bake for 18-22 minutes, or until a toothpick inserted into the cake part (not the jam) comes out clean. Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.

While cupcakes cool, make the frosting. In a large bowl, beat the softened butter until creamy. Gradually add the sifted powdered sugar, lemon juice, vanilla, and salt. Beat on medium-high speed for 2-3 minutes until light and fluffy.

Once cupcakes are completely cool, pipe or spread the lemon frosting onto each cupcake. Garnish with a fresh raspberry and a sprinkle of lemon zest.