Step 1: Preheat your oven to 350°F (175°C) and grease and flour two 8-inch round cake pans. Line the bottoms with parchment paper.
Step 2: In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt. Set aside.
Step 3: In a large bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy (about 3-5 minutes). Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract and lemon zest.
Step 4: In a separate small bowl or measuring cup, whisk together the buttermilk and fresh lemon juice.
Step 5: Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk mixture, beginning and ending with the dry ingredients. Mix on low speed until just combined, being careful not to overmix.
Step 6: Divide the batter evenly between the prepared cake pans. Bake for 28-32 minutes, or until a wooden skewer inserted into the center comes out clean.
Step 7: Let the cakes cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely.
Step 8: For the lemon cream cheese frosting, beat the softened cream cheese and unsalted butter together in a large bowl until smooth.
Step 9: Gradually add the powdered sugar, one cup at a time, beating until fully incorporated.
Step 10: Beat in the fresh lemon juice and lemon zest until the frosting is light and fluffy. If too thick, add a tiny bit more lemon juice or milk.
Step 11: Once the cake layers are completely cool, frost the top of one layer, place the second layer on top, then frost the top and sides of the entire cake. Garnish with fresh lemon slices or zest if desired.
Step 12: Refrigerate the cake for at least 30 minutes before serving to allow the frosting to set.