In a Dutch Oven, heat up vegetable oil on high heat. Once hot, Add the red onions and cook for 4-5 mins or until tender, but not caramelized. Add the garlic, ginger paste, curry, garam masala, half of the salt and red pepper flakes. Cook for 2 minutes. Add the tomatoes and cook another 4-5 minutes. Add the sweet potatoes and cook another 4-5 minutes. Add chicken broth and bring to a light boil then immediately reduce heat to a simmer. Let simmer with lid on for 15 minutes.