In a large flame-proof casserole or Dutch oven, set the potato slices on the bottom. Scatter the bell peppers, garlic, and jalapeño pepper on the potatoes. Sprinkle with salt. Place the fish on top and sprinkle it with paprika and salt. Add the tomatoes and cilantro or parsley.
Pour the water in at the edges. Sprinkle the top with oil and sprinkle generously with salt.
Set the pan over high heat, cover, and bring the mixture to a boil. Reduce the heat slightly and simmer for 25-30 minutes or until the vegetables are tender and the fish is cooked through. Check the pan after 20 minutes; if there seems to be too much liquid, uncover the pan for the remaining cooking time. Serve hot or warm with challah.