Arrange the potatoes and onions in a large roasting pan. Sprinkle with salt, pepper, and caraway seeds. Place the pork belly (rind-side up) on top and season it with salt, pepper, and caraway seeds.
Pour roughly 1 cup of water around the meat. Place in an oven preheated to 225°C (437°F) and roast for about 2 hours. Monitor the crust—if it browns too quickly after 1 hour, reduce heat to 200°C (392°F) for the remaining time.
Check that the pork has reached an internal temperature of 63°C (145°F).