In a bowl, combine the shredded Monterey Jack and cheddar cheeses. Add the chopped roasted Hatch green chiles, diced onion, garlic powder, cumin, salt, and pepper. Mix until well combined.

1. Heat a large skillet or griddle over medium heat and drizzle a little olive oil in the pan. Place one flour tortilla in the pan and evenly spread half of the cheese and chile mixture over it. Top with the second tortilla.
2. Cook the quesadilla for about 3-4 minutes on each side, or until the tortillas are golden brown and crispy and the cheese has melted. Use a spatula to carefully flip the quesadilla halfway through to ensure both sides are evenly cooked.
3. Once cooked, remove the quesadilla from the pan and let it cool for a minute. Slice into wedges and serve with sour cream or salsa, if desired.