In a large electric skillet on medium heat, sear sliced onions in Extra Virgin Olive Oil until softened.
Add Minced garlic and cook an additional 1-2 minutes
Turn heat to low, add halved cherry tomatoes and season with garlic salt and red pepper flakes
Pile fresh spinach on top of tomatoes and cover for 4-5 minutes
Fold sliced grilled chicken and fold into spinach and tomato mixture
Cook pasta according to package directions in heavily salted water
Fold cooked pasta into spinach mixture, add butter and additional garlic salt/red pepper to taste and let it sit for 5-10 minutes.
Top with crumbled Feta Cheese when serving