This is more of a condiment than a proper stew.
3 T butter, or use all oil
1 T vegetable or olive oil
1 lb onions, thinly sliced
2 1/2 lbs unpeeled apples
1/2 c raisins
1/2 c cider vinegar; or rice vinegar; or white wine vinegar
1 t (freshly ground) black pepper
1 1/2 t salt
2 T sugar, or to taste, or none at all
1. Melt butter in large skillet over medium heat with oil. When hot, add onions and sauté until onions are lightly browned, around 8 minutes.
2. Meanwhile, cut apples in half, core them, then cut them into 1/8 inch-thick slices. You don’t have to peel the apples. The skin will give some chewiness and texture to the stew.
3. Add apples, raisins, vinegar, pepper, salt, and sugar and cook, covered, 10 minutes, tossing occasionally. If there is a lot of liquid left in bottom of pot, uncover and cook 2 to 3 minutes over high heat to reduce the liquid.