In a food processor, pulse the spring onion, red pepper and water for a few seconds. Add in the chopped plantain and blend more until quite smooth.
Transfer the mixture to a mixing bowl and add in the flour, baking powder and salt. Mix until well combined. Cover the bowl with clingfilm and let the dough rest for 20 minutes.
In a wok or a sauce pan, heat the oil. You can test to see if the oil temperature is ready by dropping a little drip of the dough into the oil. If it floats immediately, not sinking to the bottom it's ready!
Scoop 5 or 6 small portions of the dough with a spoon and gently drop into the hot oil, turn the heat to medium. Please do not try frying all of the dough at the same time! Turn them around to cook them evenly.
When they are golden, take them our on a wire rack or kitchen paper to drain the excess oil. Repeat the step to deep fry the remaining dough. Fried plantains should be crispy in places on the outside.
Let them cool a little bit before serving.