Heat peanut oil in a Dutch oven over medium heat; add onion, and sauté 5 minutes or until tender. Add tomato and next 7 ingredients; cook over medium heat 4 minutes. Add coconut milk and next 5 ingredients; bring to a boil, reduce heat, and simmer 5 minutes.
Cut calamari into 1-inch pieces; add to curry sauce, and cook over medium heat 2 to 3 minutes or until calamari is opaque. Serve with rice. Garnish, if desired.