Cut acorn squash in half from stem to tip and scrape out seeds; set aside.
In a heavy, non-reactive (such as enameled) skillet, melt the butter over medium heat. Sauté onion for 2-3 minutes.
Quick trick: Use one of those handy green peeling/coring/slicing units that attach to the counter with suction. You can find these at most stores for around $20—if you don’t have one, I recommend getting one. They work really well, and save lots of time!
Core and slice the apple with the peeling arm wedged out of action. Slice the spiral to form small, uniform dice.
Add the apple, garlic and curry powder to the skillet. Sauté, stirring, for about 3 more minutes, or until apple is beginning to soften and curry has become quite fragrant.
Add lamb and mix thoroughly, breaking up chunks. Brown lamb and stir in cumin, cayenne and salt.
Add cream; allow to boil and reduce until thick.
Pack as much of the lamb mixture as possible into the hollowed-out squash halves. Place the squash in a baking dish just large enough to hold them upright.
Pour 1 inch of boiling water in the dish and cover tightly. If baking in the oven, use foil. If microwaving, use microwave-safe plastic wrap, ventilated with 2 slits.
Bake in preheated 400 F degree oven for 1 hour, or at 70% power in microwave for about 25 minutes, until the flesh of the squash is tender when pierced with a fork.