1Pierce a sweet potato with a fork and place in a microwave-safe bowl; heat in microwave until tender, 5 to 10 minutes. Cool and measure out 3/4 cup sweet potato, reserving the rest for another use.
2Preheat a waffle iron according to manufacturer's instructions.
3Combine flour, baking powder, cinnamon, and salt together in a large bowl.
4Mix sweet potato, eggs, melted butter, brown sugar, lime juice, vanilla extract, and grated lime zest together in a bowl. Pour sweet potato mixture into the flour mixture; stir until batter is smooth.
5Spoon batter into the waffle iron and cook according to manufacturer's instructions until golden brown, about 5 minutes. Repeat with remaining batter.