28 mins
Heat remaining 1 tablespoon vegetable oil in a large skillet over medium-high heat. Add onion and fry until onion has softened and turned translucent, about 5 minutes. Add bell pepper and garlic and cook for another 2 minutes. Add curry powder, cumin, coriander, and turmeric; cook for 1 minute, stirring constantly to prevent burning. Add tomato puree and sugar and bring to a boil. Lower heat slightly, and simmer until sauce reduces, adding water as needed to maintain a thick consistency, about 20 minutes.