In a 4-quart saucepan over medium-high heat, melt 2 tablespoons butter. Add onion and cook until translucent. Reduce heat to medium and add garlic, stirring frequently until garlic is soft, about 2 to 3minutes. Stir in water, then add garam masala, paprika, coriander, cumin, chili powder and cayenne pepper; cook 5 minutes, stirring occasionally. Add tomato paste, masala sauce, red chili paste and tomato. Reduce heat to low and simmer30 minutes.