Preheat the oven to 350°F (175°C). Line a standard cupcake tray with paper liners and set aside.

In a small mixing bowl, whisk together the eggs, sour cream, vanilla extract, and vegetable oil until smooth and creamy.

In the bowl of a stand mixer fitted with the paddle attachment, combine the cake flour, granulated sugar, baking powder, baking soda, salt, lemon zest, and softened butter. Beat on high speed until the mixture achieves a sandy texture.

Gradually incorporate the wet ingredients into the dry ingredients, mixing until just combined without overworking the batter.

Purée the 6 ounces of fresh raspberries in a food processor or blender until smooth. Press the purée through a fine-mesh sieve to remove the seeds, collecting the liquid. You should have approximately 1/2 cup of raspberry juice; if the yield is short, add a splash of water to reach the measurement.

Gently fold the raspberry purée into the cupcake batter, stirring until the color is evenly distributed.

Spoon the batter into the prepared cupcake liners, filling each about halfway. Lightly toss the remaining whole raspberries in flour to prevent sinking, and gently press two raspberries into the top of each cupcake.

Bake for about 25 minutes, or until a toothpick inserted into the center comes out clean. Remove the cupcakes from the pan immediately and allow them to cool completely on a wire rack.

In a large bowl, using a hand mixer or a stand mixer fitted with the whisk attachment, whip the cold heavy cream on high speed. Continue whipping as the cream first bubbles and then thickens, eventually forming stiff peaks that hold their shape when the whisk is lifted.

Once the cream has thickened, sift in the cocoa powder and sugar, folding gently until fully combined and smooth.

Once the cupcakes are completely cool, pipe or spread the chocolate whipped cream generously on top.