Preheat a coking pan on medium-high heat, add the butter and sliced onions. Saute the onions until nicely browned and caramelized. (Don't walk away too far and stir often so you don't burn the onions.)
In a medium bowl, mix all the ingredients except for caramelized onions until smooth.
Fold in the onions and transfer the mixture into an oven-safe dish. Sprinkle with a little extra shredded cheese on top.
Bake for 15-20 minutes.
Recipe from Lyuba @ willcookforsmiles.com. All images and content are copyright protected. Please do not use my images without prior permission. If you want to share this recipe, please simply link back to this post for the recipe. Thank you.