In a large skillet, melt the butter over medium heat. Add the sliced onions and a pinch of salt, cooking for 15-20 minutes. Stir occasionally until the onions become soft and golden brown. You can add a little sugar to help with the caramelization if desired.
In the same pan, add in some butter, garlic and let it cook till fragrant. Add in heavy cream, beef stock over medium-low heat. Add in all the spices. Let it simmer till it thickens.
Add in the caramelized onions back with some pasta water, cheese and mix.
Add in the cooked pasta and mix very well.
Top with some toasted bread pieces.
Enjoy while warm!