Preheat oven to 350°F (175°C). Butter and flour two 8-inch round cake pans. Line the bottoms with parchment paper rounds for easy release.

In a large bowl, cream together the softened butter, granulated sugar, and lemon zest until light and fluffy. Scrape down the sides of the bowl as needed.

Beat in the egg yolks one at a time, then stir in the vanilla extract.

In a separate bowl, beat the egg whites until soft peaks form. Set aside.

In another bowl, whisk together the flour, baking powder, salt, and baking soda.

Add the dry ingredients to the butter mixture alternately with the Greek yogurt, mixing until just combined. Scrape down the bowl between additions.

Gently fold the whipped egg whites into the batter until no white streaks remain. Be careful not to overmix.

Carefully fold in the frozen raspberries.

Divide the batter evenly between the prepared cake pans and smooth the tops with an offset spatula.

Bake for 25-30 minutes, or until a wooden skewer inserted into the center comes out clean and the cake springs back when lightly touched.

Let the cakes cool in the pans for 10 minutes before inverting them onto a wire rack to cool completely.

While the cakes cool, prepare the frosting: In a large bowl, cream together the softened butter and sifted confectioners' sugar. Add the lemon juice and optional food coloring, beating until smooth and creamy. Add more sugar for a stiffer frosting or more lemon juice if it's too stiff.

Once the cakes are completely cool, frost the cake. Place one layer on a serving plate, spread a generous amount of frosting on top, then place the second layer on top. Frost the top and sides of the entire cake.