For the filling: Heat the oil in a large skillet. Add the ground beef and cook until browned. Next add the onions and garlic; stir for 1 minute. Add the tomatoes, cumin and 1/2 teaspoon salt and black pepper. Cook, stirring constantly, until the filling is dry, 10 to 15 minutes. Set aside to cool.
For the salsa ranchero: Heat the oil in a skillet until hot. Add the tomatoes, bell peppers, onions and garlic. Cook until the onions are browned, about 2 minutes. Add the canned tomatoes and simmer until the sauce is lumpy, 10 to 15 minutes.
For the poblanos: Roast the poblanos over a gas flame, turning until blistered and slightly charred all over. Place in a heavy plastic bag and set aside for 10 to 20 minutes to steam. Scrape the skin off the poblanos. Carefully make a lengthwise slit in each poblano and remove the seeds and membranes; rinse and drain well, using paper towels to pat the poblanos dry.
Stuff the poblanos with the filling and top with salsa ranchero. Before serving, garnish with shredded cheese and cilantro.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.