Adding too much lemon juice to a recipe can cause the finished product to taste overly sour and bitter. Even a little extra acid can take over in a dish, knocking off the flavor balance. Because you can't remove the lemon juice from the dish, you'll have to try to balance it with other flavors. Adding sweetness to a recipe can cut acidity considerably, especially in sauces. Any type of sweetener, including honey, sugar and maple syrup, will work for this method.
Taste the dish as-is to gauge the flavor. Knowing how acidic the food is at the start will help you when cutting down the lemon juice flavor.
Select a sweetener for the dish. Take the temperature of the item into consideration first. Hot foods can tolerate granulated sugars as well as liquid sweeteners such as honey because they will melt the sugar crystals. Cold foods require a liquid sweetener. You'll also want to balance out the flavors in the dish. For example, sugar would work well in a tomato-based pasta sauce, but honey may be a better bet for barbecue sauce.
Add an amount of sweetener that's equal to a third of the lemon juice in the dish. For example, if the dish contains 3 tsp. lemon juice, pour in 1 tsp. of sweetener to start. Then taste the dish to see if the acid is cut sufficiently.
Add more sweetener, about a teaspoon at a time, until the lemon juice flavor is diluted to your satisfaction. The dish will not taste exactly the same as it would have if it had been made with less acid, but the addition of the sweetener should cut back on the tartness.