Peel the bananas and cut each one in half crosswise. If you prefer smaller pieces, cut each half lengthwise into halves so you have 8 batons. Pat the banana pieces dry with paper towels to remove excess surface moisture—this helps the batter adhere and prevents hot oil splattering.

Make the batter

In a medium mixing bowl, whisk together the all-purpose flour, cornstarch, granulated sugar, sea salt, baking powder, and ground cinnamon (if using) until evenly combined. In a separate small bowl, whisk the egg, milk, and vanilla extract until smooth. Pour the wet mixture into the dry ingredients and stir until just combined. The batter should be thick enough to coat the back of a spoon; if it seems too stiff, add up to 1 tablespoon more milk. If it’s too thin, add 1 tablespoon more flour.

Frying

Heat oil in a heavy-bottomed saucepan or deep skillet to 350°F (175°C). Use a thermometer to maintain temperature; if you don’t have one, test by dropping a small bit of batter — it should sizzle and rise to the surface steadily without burning immediately.

Working in batches to avoid crowding, hold a banana piece by one end (or use a skewer/tongs), dip it into the batter ensuring an even, full coating, and allow excess batter to drip back into the bowl. Carefully lower the coated banana into the hot oil.

Fry for 2 to 3 minutes, turning once with tongs, until the coating is golden brown and crisp. Smaller/thinner pieces may cook in about 1.5–2 minutes. Remove with a slotted spoon or spider and transfer to a wire rack or paper-towel-lined plate to drain. Repeat with remaining bananas, keeping cooked fritas in a warm oven (200°F / 95°C) if desired.

Finish & serve

While still warm, lightly dust the fried bananas with powdered sugar or sprinkle with coarse cane sugar for a crunchy finish. Optionally squeeze a little lime or lemon over them to add a bright contrast to the sweet fried exterior.

Serve immediately while crisp, either alone as a snack or with vanilla ice cream, dulce de leche, or a drizzle of honey/chocolate sauce if desired.