Preheat the oven to 350ºF (177ºC). Grease and flour two 8" round baking pans
In a medium size bowl, toss together the flour, baking powder, and salt
In a large bowl with a mixer, beat the butter, sugar, and lemon zest on medium-high speed until light and fluffy
Add each egg, one at a time, beating on medium-high speed until fully incorporated, scraping down the sides as necessary. Add the vanilla extract and beat again until combined
Stir the lemon juice into the milk. Scrape down the sides of the mixer bowl and turn the mixer speed to low
Add the flour in 2 additions, alternating with the milk/lemon juice. Remove bowl from mixer and stir with a spatula until everything is completely combined
Spoon batter evenly into prepared pans and bake 28-34 minutes or until lightly browned on top and a toothpick inserted in the center comes out clean
Remove from oven and allow cakes to cool in the pans completely on a wire rack before removing and assembling
Place one layer, bottom side up, on a plate or cake stand. Using a large zip top bag with the corner snipped off, pipe a well with cream cheese frosting around the outside edge of the cake Fill the cake with lemon curd, then place second layer on top, cut surface down. For a sturdier cake, refrigerate at this point for about 10 minutes. When cake is slightly chilled, remove from refrigerator and spread more frosting on the top and around the sides. Refrigerate frosted cake at least 30 minutes before cutting so cake and frosting can set