Combine water and oats in a small saucepan; bring to a boil. Reduce heat and stir in banana slices and turmeric. Continue cooking until desired consistency is reached, 2 to 5 minutes more.
Remove saucepan from heat and stir in cinnamon. Stir oatmeal and cover saucepan; let sit until thickened, about 2 minutes.
Transfer oatmeal to a bowl and top with peanut butter.
