2 tablespoons extra-virgin olive oil
1 small yellow onion, peeled, halved, and sliced into 1/4-inch-thick slices
1 teaspoon red pepper flakes (or to taste ( we started with 1/2 teaspoon)
2 (28 ounce) cans whole tomatoes
1 1⁄2 cups water
1⁄4 cup loosely packed fresh basil leaf
kosher salt
fresh ground black pepper
creme fraiche, for garnish (optional)