Start by peeling the tomatoes. To do this, boil some water in a pot then use a sharp knife to scar X-shaped cuts at the top of each tomato. Next, place the fresh tomatoes into the pot for about 60 seconds.
Meanwhile, separately fill a large bowl with ice-cold water. Use kitchen tongs to carefully remove the tomatoes from the pot and slide them into the bowl with the ice-cold water. Peel and deseed the tomatoes (the skin should now easily come off).
Transfer the tomatoes to a chopping board, allow to slightly cool then chop into quarters. Next, place the peeled tomatoes in a large bowl and use your hands to crush them.
Set the saucepan to heat under medium heat. To the pan, add the olive oil and slivered garlic. Allow the garlic to sizzle for about a minute, then stir in the peeled and crushed fresh tomatoes, onion, water, salt, red chili pepper flakes, oregano, the sprig of basil, then stir.
28 ounces tomatoes, 1 red or white onion, ¼ cup extra virgin olive oil, 1 large sprig basil leaves, 1 teaspoon dried oregano, 1 teaspoon red chili flakes, 1 teaspoon salt, ½ cup water
Reduce the heat to a low, cover, and cook for a further 25 minutes, stirring from time so the marinara does not burn. I recommend covering as it helps the tomatoes to sweat, so they break down easily. Once cooked, remove the basil and onion and set them aside in a bowl.
Add more salt if needed, garnish with some thinly sliced basil leaves and serve.