Preheat your waffle iron according to the manufacturer's instructions.
In a medium mixing bowl, mash 1 medium ripe banana with a fork until mostly smooth (small lumps are fine).
Add 2 tablespoons light canola or vegetable oil and 2 large eggs to the mashed banana; whisk until well combined.
In a separate bowl, whisk together 1 3/4 cups all-purpose flour, 1 tablespoon baking powder, 1/4 teaspoon salt, 3 tablespoons granulated sugar, and 1/2 teaspoon ground cinnamon until evenly distributed.
Add the dry ingredients to the banana mixture and stir gently until just incorporated — do not overmix.
Gradually pour in 1 1/3 cups milk while stirring until the batter is just smooth and free of large lumps.
Let the batter rest for 5–10 minutes.
If your waffle iron requires greasing, follow the manufacturer's recommendation. Pour the appropriate amount of batter onto the preheated waffle iron and cook according to the manufacturer's instructions until the waffles are golden and crisp.
Transfer cooked waffles to a wire rack to keep them crisp while you finish cooking the remaining batter.
Serve the waffles warm.