Carrabba's Lemon Butter Sauce

12 tablespoons cold unsalted butter, cut into ½ inch pieces, divided
2 tablespoons finely chopped yellow onion
2 garlic cloves, minced
1/3 cup dry white wine
3 tablespoons fresh lemon juice
Kosher salt and ground white pepper

Place a medium non-stick skillet over medium heat, add 1 tablespoon of butter. Allow the butter to melt, add onion and garlic and cook stirring frequently. Cook until onion is translucent, about 3 minutes. Add the wine and lemon juice and bring to a boil over high heat. Continue to cook until the liquid is reduced to about ¼ cup, about 3-5 minutes.
Reduce the heat to low, add 3 tablespoons of butter at a time and whisk the butter in until it is completely melted. You want the butter to slow soften into an emulsified sauce, not quickly melting it is a process. Add the remaining butter 3 tablespoons at a time until all the butter has been added into the sauce. Season the sauce with salt and pepper, then remove from heat.
Serve immediately or store sauce upto 2 hours at room temperature. If you are to reheat the sauce do it over a low setting, otherwise the sauce will separate.
If it does separate remember the sauce will still taste the same, just not have the same look, it will look more like melted butter. Don’t worry after a few times of making the sauce you will get the hang of it.
Cooking this sauce on low heat is key.