Barbara Lynch's Spicy Tomato Soup

INGREDIENTS

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