Line the cake pan with parchment paper. If the pan has a detachable bottom, cover the bottom cover with aluminum foil to prevent water leakage as it'll be baked in a water bath.
Strain the yogurt overnight. A pack of 500 g yogurt weighed 170 g after straining.
Preheat the oven to 160ºC. Pour water in a rimmed baking pan, and pop it in the oven (so that you don't need to pour boiling water into it).
Wash the lemon well, grate the zest, and squeeze the juice.
Add the egg yolks, skim milk powder, and katakuriko into the yogurt and mix.
Whip up a stiff peak meringue by adding sugar into the egg whites in three batches.
Mix the meringue into the yogurt mixture in three additions.
Add lemon juice and zest into the bowl from Step 5 and mix.
Pour the batter into the pan, and spin it around to flatten the surface.
Steam-bake in the water bath for 60 minutes. If the surface starts to scorch, cover with aluminum foil.
The surface is cracked right out of the oven, but it will deflate and settle with time.
When it has cooled, chill in the refrigerator overnight. The surface is not even, but enjoy it.
Story Behind this Recipe
I wanted to use up expiring yogurt.
Lemon is the key to this recipe, so use an entire lemon, including the peel Strain the yogurt well! I am too lazy to sift the flour so I planned to use corn starch...but I had run out, so I used katakuriko and it worked out!