When a recipe calls for you to saute onions and garlic together, saute the onions first for at least 1/2 of their cooking time before adding the garlic. If you start them at the same time, the garlic cooks faster and has a tendency to burn and overcook, causing your dish to come out tasting bitter. Once you burn garlic, you can’t get that taste to go away by adding anything else to counter act it.
Check out this tip on How to Remove Onion and Garlic Smell from Your Hands!
Be sure to check out my other Cooking Tips!