These Rhubarb Muffins with Greek Yogurt are a delightful treat perfect for breakfast or a snack. Combining whole-wheat and all-purpose flours gives these muffins a hearty texture, while the fresh diced rhubarb adds a tart, refreshing burst of flavor. Greek yogurt keeps the muffins moist and tender, complemented by a cinnamon-sugar topping for a subtle crunch.