Instructions:
Preheat Oven: Preheat your oven to 350°F (175°C). Line a square cupcake pan with parchment paper or silicone liners, or lightly grease the pan and set aside.
Prepare the Cupcake Batter: In a large mixing bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and sour cream until well combined.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, alternating with the milk, beginning and ending with the flour mixture. Fold in the lemon zest.
Add Raspberries: Gently fold in the fresh raspberries, being careful not to overmix and break them.
Assemble the Swirl: Pour half of the cupcake batter into each square cupcake mold, filling about halfway. Dollop the raspberry preserves and lemon curd over the batter and swirl gently with a knife. Add the remaining batter to each mold, filling them to about three-quarters full.
Bake: Bake in the preheated oven for 20-25 minutes or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely in the pan on a wire rack.
Prepare the Frosting: In a medium bowl, beat together the cream cheese and butter until smooth and creamy. Gradually add the powdered sugar, lemon juice, and vanilla extract, and continue to beat until well combined. If desired, add a few drops of yellow food coloring for a vibrant color.
Frost the Cupcakes: Once the cupcakes are completely cool, pipe or spread the lemon cream cheese frosting on top of each square cupcake. Garnish with fresh raspberries.
Serve: Enjoy these delightful square cupcakes at any gathering or as a sweet treat!