Heat the oil in a medium pot or pan over medium-high heat. When the oil begins to swirl, add the tomatoes and capers and cook, stirring intermittently, so the tomato skins begin to sear and brown. Once the skins begin to burst, add the onions and red chili flakes. Season everything with a pinch of salt and a few grinds of black pepper. Cook, lightly stirring, until the onions are tender and the tomatoes release their juices, mashing them gently as you stir. Add the tomato paste, basil and garlic. Stir and cook until the tomato paste blends into everything, about 5 minutes. Lower the heat and simmer until the garlic is tender, about 10 minutes.
Remove the basil leaves and discard. Pour the contents into a blender or use an immersion blender to blitz everything until smooth. Refrigerate and serve chilled as a dip.
Perfect for kabobs, crudite, breadsticks and anything that needs a tomato kick!
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.