Grease your 6-inch cake pans, then line the bottom with a 6-inch circle of parchment. I do this by sitting the cake pan on a piece of parchment, tracing it, and cutting it out.
Preheat oven to 325 degrees.
Sift together your flour, sugar, baking powder, and salt in a medium-sized bowl.
Form a well in the center of the dry ingredients. In the well, add in your water, oil, egg yolks. vanilla, lemon zest, lemon juice.
Mix to combine.
In a CLEAN bowl with a CLEAN whisk or hand mixer, whisk the eggs whites and cream of tartar to stiff peaks.
Fold about ¼ of the egg whites into your cake batter. Folding carefully.
Fold in this rest of the egg whites until they are all incorporated. Be careful not to deflate the egg whites very much.
Divide the batter between the pans, either 3,6-inch, or 2,8-inch.
Move to oven and bake for about 30-45 minutes. The cake will be a light golden brown and a toothpick inserted comes out clean.
Remove from the oven and allow them to cool on a cooling rack for about 10 minutes.
Run a knife around the edges and remove them from the pan. These cakes were small enough I turned them out onto my hand, then right side up on the cooling rack.
If that makes your nervous, set a cooling rack on top and remove that way.
Allow the cakes to cool.
Once they are cooled, start the buttercream.
Add the butter, powdered sugar, and vanilla to a bowl. Start by adding 2 tablespoons milk. Mix on high speed until well blended. Check the consistency. If you want to a add more milk, do it.
Level your cake tops. What that means is cut off the top where is had domed to level it. This makes it so much easier to stack the layers, so don't skip this step!
Pipe your buttercream around the top edge of the bottom cake.
Fill inside the piping with the lemon curd. I used about ⅔ cup in mine.
Stack the next 2 layers, repeating this process with each layer.
On the last, top layer, top with your chopped strawberries.