In a large pot, bring the water to a boil and add 1 tablespoon salt, crushed garlic, and chopped large onion.
Add the chicken leg quarters and simmer uncovered for about 30 minutes, skimming any foam that forms on top.
Meanwhile, in a skillet, heat cooking oil over medium heat and sauté the thinly sliced onions until translucent and golden.
Add the chopped tomatoes, ground cumin, mild paprika, and a pinch of salt to the onions; cook until tomatoes break down and create a flavorful sauce, about 8-10 minutes.
Add the sautéed onion and tomato mixture to the pot with the chicken.
Add the peeled and cut cassava, plantains, and potatoes to the pot. Cover and simmer gently for 40-50 minutes, or until the vegetables and chicken are tender.
Adjust seasoning with salt to taste, then stir in the chopped fresh cilantro just before serving.
Serve hot, ladled into bowls with some broth, chicken, and vegetables in each serving.