Heat a large, deep nonstick sauté pan over medium heat. Add the diced onion and a pinch of salt and cook for 1 minute, stirring occasionally. Then add the water and bring the mixture to a simmer. Cook for 5 minutes, or until the onion has softened and the water has just evaporated, stirring frequently to prevent burning.
Add the drained beans and stir to combine. Pour in the coconut milk, tomato sauce, 1 teaspoon kosher salt, black pepper to taste, and white beans. Stir to combine and coat all of the beans in the sauce.
Add the kale and stir again to incorporate. Bring the mixture to a rapid simmer, then cover with a lid. Continue to cook at a rapid simmer for 10-15 minutes or until the sauce has thickened. Season to taste with salt as needed. If desired, serve over cooked millet, quinoa, or brown rice.