Place the tomato and onion in a fine-meshed sieve with a bowl underneath, toss with 1 teaspoon of salt flakes and allow to sit for 30 minutes to release their liquid. Discard the liquid.
Place the tomato and onion mixture in a bowl and add the herbs, cinnamon, flour, baking powder and feta.
Season with salt flakes and cracked black pepper and mix to combine until the mixture is a little sticky and just holds together.
Set aside in the fridge for 30 minutes to allow the mixture to soften and slightly set.
Heat the olive oil in a large non-stick frying pan over medium heat.
Working in batches, add heaped tablespoons of the tomato mixture to the pan and cook for 4-6 minutes, turning halfway through cooking, until golden and crispy.
Remove with a slotted spoon and drain on paper towel.
Scatter the tomatokeftedes with yogurt and serve.
