The fritter mixture is better to be used right away. Because the more it sits, the runnier it will get. Which means you will need to add more flour which in turn means a more bland flavor. So it is better used once you make it.
Remove the stems and bottoms of the tomatoes. Cut them in half, remove the insides and add them into a food processor or blender. Add the red pepper in as well and blend until smooth runny paste forms.
Transfer this paste into a non-stick pan along with the 2 tablespoons of olive oil. Cook over high heat for about 5 minutes stirring with a wooden spoon until it drains and thickens.
Cut the skins of the tomatoes into very small dices and add to a mixing bowl.
Add the spring onion, red onion, the cooked tomato paste, dried oregano, and chopped basil into the bowl as well. Season with salt and pepper. But don't add too much salt as the feta is salty enough.
Stir to combine and then add the feta cheese. Add also the flour in the mixture in batches while stirring the mixture with a spoon. You may need more or less flour depending on the moisture of your mixture and how ripe the tomatoes are. The mixture should be thick like a cake batter or sticky enough to hold the ingredients together. It may get runnier while it sits so you may need to add a tablespoon or two of extra flour by the time you have fried all of the fritters.
Half-fill a non-stick pan with frying oil (about 2cm in height) and heat over medium-high heat.
Once the oil is sizzling hot, take spoonfuls of the fritter mixture (using a tablespoon) and add them into the hot oil. Keep some distance between each fritter so they won't stick together. Don't cook more than 5-6 at a time because the temperature of the oil will drop and the fritters will get soggy. Cook the fritters for 3-4 minutes, flipping them once or twice until they get a deep-golden color all around.
Transfer fritters on paper towels to drain excess oil. Again, leave some space between them so there is room for excess moisture to escape.
Serve warm with the cold yogurt dip.