Melt butter in a skillet over medium high heat until foamy.
Add minced garlic and cook for 1-2 minutes, whisking occasionally.
Whisk in lemon juice.
Remove 2-3 tablespoons of the butter sauce to a measuring cup. Add cornstarch to the measuring cup and whisk well.
Add butter cornstarch mixture back to the skillet and whisk over medium-high heat until bubbly. Simmer over low heat for 2-3 minutes.
Notes
Jarred minced garlic is convenient when making this sauce, but you can certainly use fresh minced garlic as well. In fact, it will add even more flavor! You will need 8-9 cloves to yield 3 Tablespoons minced.
To yield 2 Tablespoons of juice you will need 1 lemon.
Although this sauce is best served right away, you can store any leftovers in an air-tight container kept in the refrigerator for up to 5 days. The butter will solidify when refrigerated. To reheat, spoon the mixture into a skillet over medium-low heat stirring often until warmed through. You can also reheat the sauce in the microwave in 20-second increments.
Adding some fresh herbs to your butter sauce adds another delicious flavor element. Consider fresh basil for pasta noodles or for dipping garlic bread. Fresh dill would be a nice addition for spooning over fresh fish.