Sauté the finely chopped onion and garlic well in olive oil.
Add the cherry tomatoes and cover for 2 minutes.
Meanwhile, in two to three batches, place the chopped tomatoes in a tall measuring cup, adding a splash of water each time. Blend until smooth and add to the cherry tomato mixture.
Season with salt and piri-piri peppers (or chili flakes) and let simmer for 1 hour.
Pour into jars and seal while still hot.
Tips
You can really control this sauce. For example, season extra with oregano or basil. You can keep the sauce in the fridge for at least a week, or freeze it. This way you always have a wonderful basis at hand to make something quickly.