First, rinse the beans under cold water. Then, soak the beans in water for at least 8 hours (overnight).
Drain the beans and transfer to a medium-sized pot. Add 6 cups of fresh water. Bring to a boil, then let simmer for 1 hour. Over the course of the hour, add an additional 2 cups of water as needed.
When the beans look soft and broken down, use an immersion blender to blend until the beans are just broken up--it shouldn’t be completely smooth (unless that’s your preference--you’re the cook here!). You can also transfer to a blender and pulse a few times until you achieve your desired consistency.
Transfer the blended mixture back to the pot. If you like a soupier consistency, feel free to add additional water at this stage until you reach your desired consistency. Add the sugar and orange zest. Stir over medium to medium-high heat to dissolve the sugar. The mixture should bubble very gently.
Next, add the tapioca. Cook for 20 minutes until the tapioca pearls become translucent. Some recipes recommend cooking the tapioca separately, but it works just fine to add them directly to the soup. When the tapioca pearls are totally translucent, it’s ready to serve!