In a dutch oven over medium heat, melt the butter or warm the avocado oil, then add in the onions. Cook 5 minutes, until softened.
Pour in the wine or broth then add salt and pepper. Continue cooking another 5 minutes, until the wine or broth has evaporated and the onions are lightly golden.
Sauté keeping a close eye and stirring constantly until the onions are the softness you prefer.