Step 1

Preheat the oven to 425°F.

Step 2

Place the tomatoes on a baking sheet and drizzle with 2 tablespoons of the olive oil. Roast for 30 minutes. Set aside to cool.

Step 3

Warm the remaining 2 tablespoons of olive oil in a medium pot over medium heat. Add the onion with ½ teaspoon salt and saute until soft and translucent, about 5 minutes.

Step 4

Transfer the tomatoes and onion to a blender or food processor (or use an immersion blender) and pulse until smooth. Return the sauce to the saucepot and add the basil, water, 2 teaspoons salt, and pepper. Simmer over medium heat for 5 minutes to marry the flavors. Serve hot or transfer to the refrigerator for up to 1 week.