Heat the olive oil in a large, deep skillet over medium heat.
Add the onion and garlic and cook for 1 to 2 minutes, or until fragrant and just starting to soften.
Combine the chili powder, paprika, cumin, brown sugar, salt, and pepper.
Add the chicken and spice mixture to the pan.
Cook, stirring often, until the chicken is cooked through and no longer pink in the center, about 5-7 minutes.
Next, stir in the pasta, chicken stock or water, and enchilada sauce.
Raise the heat to high to bring to a boil for 10-12 minutes, or until the pasta is al dente.
Remove the pan from the stovetop and mix in 1 cup of shredded cheddar cheese.
Garnish with a sprinkle of additional cheese, slices of tomato, and/or fresh cilantro, if desired.