Yes, adding a small amount of sugar or another sweetener like jaggery or honey can effectively balance the sourness in dal. Start with a small amount and adjust to taste.
When dal becomes too sour, it's often due to an excess of tomatoes, tamarind, or other acidic ingredients. Sugar works by counteracting the acidity, creating a more harmonious flavor profile. The key is to add it gradually. Begin with about 1/4 to 1/2 teaspoon of sugar for a standard pot of dal. Stir well and taste. Continue adding small amounts until the sourness is balanced to your liking. Remember that the goal is not to make the dal sweet, but to neutralize the sourness. Other sweeteners like jaggery (unrefined sugar) or honey can also be used, each adding a slightly different nuance to the flavor. Jaggery provides a more earthy sweetness, while honey offers a floral note.
If adding sugar doesn't fully resolve the sourness, consider adding a pinch of baking soda. Baking soda is alkaline and will neutralize the acid. However, use it sparingly, as too much can alter the texture and taste of the dal. A tiny pinch is usually sufficient.