Saute + Simmer. Heat 2 tablespoons oil over medium heat in a dutch oven or large pot (make sure you have a lid for this). Add onion (1 1/2 cups) and saute until soft, about 6 minutes. Add garlic (3) and ginger (2 teaspoons), and saute until fragrant, about 1-2 minutes. Add curry powder (1 tablespoon), cumin (1 teaspoon), turmeric (1 teaspoon), coriander (1 teaspoon), and cayenne pepper (start with 1/2 teaspoon, we'll adjust later), and toast another minute or two, until fragrant. Stir in the coconut milk (1 13.5 Oz can), tomatoes (3/4 cup), salt (1 1/2 teaspoon), and bring your sauce to a simmer. Simmer to marry the flavors for 5 minutes.