Sautee onion in a pan until translucent. Add split peas to spaghetti sauce, leave the peanut butter for later. Cover with water or broth 1 -2 inches above veggies and split peas. Bring to a boil, cover, and put on a medium heat. Stir every 20 min or so, adding more water as needed. When split peas are cooked (I like mine mushy, takes about 45 minutes) add the peanut butter. Stir in, leave for 5 min until its cooked in. Then add the seasonings, and let simmer for 10 - 15 min to let the seasonings cook through.
When I make this it makes about 10 cups, and mine is pretty thick. Eat over rice, couscous, throw in some croutons, whatever. I like to sprinkle some nutritional yeast over it just before I eat it.