Preheat broiler. Broil chiles for about 5 minutes on each side, or until charred. Once charred, transfer to a dish with a lid and let sit for 15 minutes. Remove skin, ribs, and seeds. Dice chiles and set aside.
Preheat oven to 350F.
Heat olive oil over medium heat in a 10-inch cast iron skillet. Add onion and cook for 2 minutes, until slightly softened. Add garlic and cook until fragrant, just 30 seconds. Add sausage and cook, breaking up as it cooks. Once cooked through, drain off excess fat and add in diced tomatoes. Cook until most of the liquid has been absorbed. Remove from heat and sprinkle green chiles on top of sausage mixture and top with both cheeses.
Bake until cheese is melted and bubbly, about 15 minutes.
Sprinkle with cilantro before serving.
Serve immediately with tortilla chips and a chilled sweet wine like Sutter Home’s Moscato.