Preheat the oven to 350°F. Line three 8-inch cake pans with parchment and spray with cooking spray.
In a large bowl or the bowl of a stand mixer, rub the lemon zest into the sugar until fragrant. Add the butter and beat until light and fluffy.
Add the eggs and egg whites, vanilla, and lemon juice, and mix until well blended.
In a medium bowl, whisk together the cake flour, salt, baking powder, and baking soda. Add the dry ingredients to the wet ingredients in three additions, alternating with the buttermilk, and mix just until combined.
Divide the batter evenly between the prepared pans and bake 23-26 minutes, until a toothpick inserted in the center comes out clean. Move to a cooling rack and cool completely before frosting.
To make the frosting, puree the raspberries using a blender or food processor. Strain the raspberries through a sieve to remove the seeds.
Add the butter to a large bowl or the bowl of a stand mixer, and beat until light and fluffy. Add the raspberry puree and powdered sugar, and mix until combined. Add cream as needed to make a smooth frosting. Beat on high speed until light and fluffy.
To assemble the cake, level each of the cake layers. Place a cake layer on a serving platter or cake stand and spread a ¼ inch thick layer of frosting over the top. Pipe a ring of frosting around the edges of the cake layer to hold in the jam. Spread ½ cup of raspberry jam evenly over the buttercream.
Repeat with the next cake layer, then top with the remaining cake layer. Spread a thin coat of frosting over and around the cake to seal in the crumbs.
Refrigerate for at least 30 minutes.
After the frosting has set, spread a thicker layer of frosting around the sides and top of the cake, then decorate as desired (I just did little dollops with an open star tip).
Refrigerate any leftover cake.