Bring a large pot of generously salted water to a boil and cook the spaghetti until al dente according to package directions; drain, toss with a little olive oil to prevent sticking, and set aside.
Heat 1 tablespoon olive oil in a large Dutch oven or deep skillet over medium-high heat. Add the diced onion and sauté about 5 minutes until softened.
Add the ground meat and cook, breaking it up with a spoon, until browned and cooked through and the onions are tender.
Stir in the tomato paste, minced garlic, chili powder, ground cumin, salt, dried oregano, smoked paprika, black pepper, and optional cayenne; cook 1 minute to bloom the spices.
Pour in 1 cup water and scrape the bottom of the pan to deglaze. Add the fire roasted diced tomatoes with their liquid, the diced green chiles, and beef bouillon; stir to combine.
Simmer the sauce, uncovered, for about 5 minutes, stirring occasionally to thicken slightly and meld flavors.
Remove the pan from heat and stir in the shredded cheddar and Monterey Jack cheeses a handful at a time until melted and the sauce is creamy.
Add the cooked spaghetti to the sauce and toss until the noodles are evenly coated; taste and adjust salt, pepper, or cayenne as desired.
Serve individual portions topped with crushed tortilla chips, extra cheese, diced tomatoes, diced avocado, chopped cilantro, and sour cream as desired.