By Yotam Ottolenghi, The New York Times LONDON — Recently, when I posted a picture of a homely, frozen-spinach-filled pie on my Instagram, it got a lot of love. Usually, it’s red tomatoes that get the red hearts. It was interesting, then, to think about why this simple pie struck such a “Yes, please!” chord. There are many words I could reach for to explain this pie’s appeal, and they’d all be true.