Preheat the oven to 350°F (175°C). Grease and flour two 9-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 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 vanilla extract.
Add the flour mixture in three additions alternating with the whole milk, beginning and ending with the flour mixture. Mix each addition just until combined.
Divide the batter evenly between the prepared cake pans and smooth the tops.
Bake for 28-30 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. Then turn them out onto wire racks to cool completely.
While the cakes cool, prepare the lemon frosting: In a large bowl, beat the softened butter until creamy.
Gradually add the powdered sugar, one cup at a time, beating on low speed until incorporated.
Add the lemon juice, lemon zest, heavy cream, and vanilla extract. Beat on high speed for 3 minutes until the frosting is light and fluffy.
If the frosting is too thick, add a little more heavy cream, one teaspoon at a time, until desired consistency is reached.
Once the cakes are completely cool, place one cake layer on a serving plate. Spread a layer of lemon frosting over the top.
Place the second cake layer on top and frost the top and sides of the cake with the remaining lemon frosting.
Decorate as desired and serve.