Cake Layers:
Preheat your oven to 350°F (175°C). Butter and flour two non-stick 8-inch cake pans, and place a round of parchment paper at the bottom of each pan for easier release.
In a large mixing bowl, cream together the butter, sugar, and lemon zest until light and fluffy, scraping down the sides of the bowl as needed.
Beat in the egg yolks one at a time, followed by the vanilla extract.
In a separate bowl, beat the egg whites until soft peaks form, then set aside.
In another bowl, whisk together the flour, baking powder, salt, and baking soda.
Add the dry ingredients to the butter mixture in batches, alternating with the yogurt, and mix until well combined. Be sure to scrape down the bowl to ensure all ingredients are fully incorporated.
Gently fold in the whipped egg whites until no white streaks remain in the batter.
Carefully fold in the raspberries.
Divide the batter evenly between the two prepared cake pans and smooth the tops with an offset spatula.
Bake the cakes on the same oven shelf for about 30 minutes, or until the center springs back when lightly touched and the edges are just starting to turn golden. Be careful not to overbake.
Allow the cakes to cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.
Frosting:
In a large mixing bowl, cream together the butter and sifted confectioner’s sugar, adding the lemon juice gradually until the frosting is smooth and spreadable. If desired, add a small drop of yellow gel food coloring for a vibrant look.
Adjust the consistency by adding more sugar for a stiffer frosting or more lemon juice if the frosting is too stiff.
Once the cakes are completely cool, spread a generous amount of frosting on the first layer. Place the second layer on top, then frost the top and sides of the cake until fully covered.