Preheat Oven to 450 degrees and line a baking sheet with foil.
Wash and dry the peppers; place them on the baking sheet. Cook in the oven for 20-25 minutes or until the skin is charred and blacken. You may want to turn the peppers after 10 minutes of cooking.
Once roasted, take the peppers out of the oven and transfer to ta zip lock bag, to steam for 15 minutes. This will loosen the skin. When cool enough to handle, remove the skin, slice in halve lengthwise and scrape the seeds out.
Turn oven down to 350 degrees.
While the peppers are roasting, saute onions and garlic in a glug of olive oil over a medium heat. Once soft, add ground beef, cumin, salt, pepper and any other spices you want. Once the beef is thoroughly cooked, drain grease and return to pan.
In a 9" baking dish, spray with a non stick cooking spray. Place four poblano pepper halves on the bottom of the baking dish, then spread half of the beef mixture on top of the peppers and then layer half of your cheese mixture. Repeat the layers once more, peppers, beef then cheese.
Bake uncovered at 350 degrees for about 30-35 minutes or until the cheese is melted and browned.
Serve with chips and an avocado salad or with rice and beans.