In a large pot, saute the onions in oil over medium heat for about 10 minutes or until they have become translucent.
Add the turmeric and stir for a couple of minutes.
Add the beef pieces and saute on high heat for about 5 minutes. The beef and onions should have turned a beautiful golden color and become aromatic.
Add water, cover, and bring to a gentle simmer before reducing the heat and cooking the stew for one hour. The beef should be somewhat tender but not fully cooked at this stage.
While the stew is cooking, saute the sliced quince in a large frying pan over medium heat with oil until they have become golden in color. Typically this would take about 2-3 minutes on each side. Remove from the heat and set aside.
After the beef has been cooking for 1 hour, add the yellow split peas, stir, cover and cook for another 30 minutes.
Add salt, pepper, sugar, vinegar and saffron water to the main pot, and stir.
Place the sauteed quince on top of the Khoresh and gently press them down enough to soak up some of the stew's cooking broth. Cover and cook on low heat for 10 minutes.
Remove from the heat and allow to sit for 5 minutes before serving.
Serve with Persian steamed basmati rice.