Step 1In a small pot, combine the coconut milk, tomatoes, salt, curry powder, sugar, cayenne pepper, lime juice and 1 cup water. Bring to a gentle simmer over medium-high heat, stirring occasionally. Thicken if desired by whisking in a little cornstarch slurry, then reduce the heat so the soup barely bubbles and cook for 15 minutes, stirring occasionally, to give the flavors time to marry. Taste and adjust the seasonings, and thin or thicken with additional water or cornstarch slurry. This makes a scant 2 quarts soup.