I will definitely make this again.  
We loved the sweet potatoes, the onions and that sauce, yum.  I did use frozen meatballs and of course, just not as good as homemade.  If I don't make my own the next time, I will just use a couple of chicken breasts cut into 1 inch pieces and put them on the sheet pan with the potatoes and onions - cover them with olive oil and spices and bake for 25 -30 minutes. Plate the whole thing with that yummy sauce and garnish with the leftover 1/2 avocado and cilantro.  It was that good!
One modification -  I did put about 1 heaping tbs of Greek yogurt in the 1/4 cup measure that I then filled with mayo....