Melt two tablespoons of butter in a large saucepan over medium heat. Add the cabbage to the pan and cook until cabbage is lightly caramelized, stirring occasionally, about 3 minutes. Add the soy sauce and water to the pan and cook for another 3 minutes until tender. Stir in the remaining tablespoon of butter and remove from the heat. Using a spatula, transfer the cabbage and butter sauce to a serving dish. Garnish with sesame seeds and serve warm.