Bring a large pot of salted water to a rolling boil. Add spaghetti and cook until al dente, around 8–10 minutes. Reserve ½ to ¾ cup of pasta water before draining.

While pasta is cooking, seed and chop the fire-roasted hatch chiles, and finely dice the onion.

In a large skillet, heat olive oil over medium heat. Add diced onion and sauté for 3–5 minutes until softened. Stir in minced garlic and cook for an additional minute.

Stir in chopped hatch chiles, vegetable broth, sea salt, and chili powder. Cook for 3–5 minutes to meld flavors.

Lower the heat and add Monterey Jack cheese and sour cream, stirring until the cheese melts. Gradually add reserved pasta water to reach desired sauce consistency.

Carefully add drained pasta to the sauce, tossing to coat. Let sit for a minute over low heat.

Distribute onto plates and garnish with chopped cilantro and crumbled cotija cheese. Serve warm.