Drain the chickpeas and rinse well with cold water. Peel and chop the onion and garlic.
Puree the chickpeas, onion, garlic, and parsley until a paste forms. Add the cumin, coriander, and turmeric, then puree again until fully combined.
Transfer the paste to a bowl. Add the flour one tablespoon at a time, stirring well with a fork after each addition. Mix in the baking powder until smooth. If the mixture is still too soft to shape, add more flour one tablespoon at a time.
Shape a tablespoon of dough into a ball between your palms.
Heat the oil in a saucepan over high heat. Test the temperature by placing a falafel in the oil for a few seconds—if it sizzles and bubbles immediately, it's ready. Remove with a slotted spoon.
Add the falafel balls to the hot oil and fry for 2-4 minutes until golden brown and crispy.
Remove with a slotted spoon and drain on paper towels.