Bucantini all' Amatriciana

Here is the recipe..Perfection, I find lots of recipes for this but this one is simple and direct and could not be better.

4 oz or so Guanciale sliced 1/4 inch thick, then cut into 1/2 wide pieces
1 med/large sweet onion chopped
Big pinch crushed red pepper flakes or to taste
1 Large can good quality crushed tomatoes (I like Progresso for this)
Fresh grated Parmasan, Percorino Romano, of choice.

1/2 LB. Bucatini

Over medium low heat render gaunciale until browned but not yet crispy. Remove from pan and remove all but about a tablespoon of the rendered oil in pan. Add onions and red pepper flakes, raise heat to medium and saute until translucent. Add tomatoes, and Gaunciale back to pan. Cook over medium until thickened.
In the meantime cook pasta until done. Add to sauce then plate. Grate cheese over and enjoy!