I have known many condiments in my lifetime, and I have known many fish. But until I enrolled in a pizza-making class in Manhattan last year, I had never known how perfect a union of the two could be. As we embellished our pies with the usual mozzarella and basil, the school's owner dug into his refrigerator and produced a jar containing a thick, slightly oily red relish. He handed me a spoon, and a few moments later my obsession with neonata began. It was fiery, succulent, and totally invigorating, with a red-pepper sweetness underscored by an anchovy funk. I slathered some on a slice and took a bite. Needless to say, it yielded a pizza like no other.