While you *can* use flavored oils for tadka, it's generally not recommended as the high heat can degrade the flavor and potentially burn the added flavorings, resulting in an undesirable taste. It's better to add the flavorings directly to the oil.
Tadka, also known as tempering or seasoning, involves heating oil or ghee and then adding spices and aromatics to infuse the oil with their flavors. This infused oil is then added to a dish to enhance its taste and aroma. Flavored oils, such as chili oil or garlic-infused oil, already contain added flavorings. When these oils are heated to the high temperatures required for tadka, the delicate flavors they contain can break down or burn, leading to a bitter or off-putting taste.
Instead of using pre-flavored oils, it's best to use a neutral oil like vegetable oil, canola oil, or ghee and add your desired flavorings directly to the hot oil. This allows you to control the intensity of the flavors and prevent them from burning. For example, if you want a garlic-flavored tadka, add minced garlic to the hot oil and sauté it until it's fragrant and lightly golden brown. Similarly, for a chili-flavored tadka, add dried red chilies or chili flakes to the hot oil.
Always start with a low to medium heat when making tadka. This prevents the spices from burning quickly and allows their flavors to gently infuse into the oil. Burnt spices will ruin the entire dish.