Peel the bananas, break them in half and place them in a large mixing bowl. Mash the bananas using a  masher or a fork. You'll notice that the mashed bananas will become runnier/looser as you mash, there will be lumps, but they should be small.

Add the cinnamon and salt to the mashed bananas, whisk until evenly combined.

Using a sifter, add the cornmeal and flour to the banana mixture. Add the baking soda and whisk everything together to form a thick batter. The batter will be lumpy, keep mixing until there are no dry patches/clumps.

Heat half of the oil in a large skillet over medium-low heat. Once the oil is hot, drop 4-6 spoonfuls of batter into the oil at time. Try to keep some distance between each of the brinhola fritters so that they don't touch. 

Cook the brinhola for about 3-4 minutes per side, or until each side is golden brown. If you notice the brinhola getting too dark, turn the flame down as needed. Use a metal spatula to flip the brinhola (it might help to use secondary utensil to push the brinhola onto the spatula) 

Drain the brinhola on a metal cooling rack (for best results) or on a plate lined with paper towels. Do not pile the brinhola on top of each other, otherwise they will become soggy.

Transfer the brinhola to a warm oven and fry the remaining batches using the remaining oil as needed. Serve on a platter and top with a dusting of cinnamon if desired.