Preheat the oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
In a large bowl, beat the softened butter and granulated sugar together with an electric mixer on medium speed until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, beating well after each addition.
Mix in the lemon zest and vanilla extract.
Alternately add the dry flour mixture and milk to the butter mixture, beginning and ending with the flour mixture. Mix each addition just until incorporated.
Stir in the fresh lemon juice until combined.
Divide the batter evenly between the prepared cake pans and smooth the tops with a spatula.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and allow them to cool in the pans for 10 minutes.
Turn the cakes out onto wire racks to cool completely.
For the lemon buttercream, beat the softened butter in a large bowl with an electric mixer on medium speed until creamy, about 2 minutes.
Gradually add the powdered sugar, one cup at a time, beating on low speed until combined.
Add the lemon juice, heavy cream, and lemon zest, then beat on high speed for 3 minutes until light and fluffy.
If desired, divide the buttercream into portions and tint with yellow and green gel food coloring for decorating.
Once the cakes are completely cool, place one cake layer on a serving plate and spread a layer of lemon buttercream on top.
Place the second cake layer on top and apply a thin crumb coat of buttercream over the entire cake.
Chill the cake in the refrigerator for 15 minutes to set the crumb coat.
Apply a final smooth layer of lemon buttercream over the cake.
Use remaining colored buttercream to pipe decorative designs or create artistic accents on the cake surface.
Garnish the cake with edible flowers or thin lemon slices if desired.
Serve and enjoy your lemon cake art!