1 (28-ounce) can whole peeled tomatoes
1 tablespoon extra-virgin olive oil
1 tablespoon unsalted butter
6 medium cloves garlic, grated on microplane grater (about 2 teaspoons)
6 minced anchovies
1 teaspoon dried oregano
pinch red pepper flakes
Kosher salt
2 (6-inch) sprigs fresh basil with leaves attached
1 medium yellow onion, peeled and split in half
1 teaspoon sugar