pumpkin-java-multiversion/assets/datapacks/26_2/data/minecraft/recipe/cauldron.json

{
  "type": "minecraft:crafting_shaped",
  "key": {
    "#": "minecraft:iron_ingot"
  },
  "pattern": [
    "# #",
    "# #",
    "###"
  ],
  "result": {
    "id": "minecraft:cauldron"
  }
}