This classic Neapolitan dish involves poaching fish in a liquid that Marcella Hazan explained as being “denser than a broth, looser, more vivacious and fresher in taste than any sauce.” It’s made by simmering chopped extra-ripe tomatoes with water, garlic, chile and other flavorings. Once the water tastes like tomato, fish fillets are poached in it. This foolproof method prevents overcooking, so it’s ideal for all kinds of delicate seafood. Some think “crazy” refers to the broth’s spiciness, while others think the name comes from the fact that fishermen made the dish with seawater (but it could also simply reflect that water is the key ingredient).
In a large skillet with high sides, combine the olive oil, garlic, fennel seeds and red-pepper flakes. Set over medium-low and cook, swirling occasionally, until sizzling and fragrant, 3 to 5 minutes.
Add 2 1/2 cups water, the tomatoes and 2 teaspoons salt to the skillet. Bring to a boil over high, then cover, reduce heat to medium, and cook until the tomatoes are softened and the water is bright red and tastes like tomato, 15 to 20 minutes.
Pat the fish dry and season with salt. Lay the fish into the tomato water, cover and cook until the fish is opaque and flakes easily, 4 to 8 minutes.
Taste the water and adjust seasonings with salt and red-pepper flakes. If the liquid has reduced so much that it resembles sauce, add a little water until it looks like tomatoes suspended in red-tinted water. Serve the fish and tomato water in shallow bowls, with a drizzle of olive oil and bread for dunking.