In a small bowl, combine ground cumin, paprika, chili powder, onion powder, garlic powder, chicken bouillon powder, and a pinch of salt and pepper; set aside.
Heat the olive oil in a large nonstick pan over medium-high heat. Add the minced garlic and cook until fragrant, about 30 seconds.
Add the reserved spice mixture to the pan and cook, stirring, for 1 minute to bloom the spices.
Stir in the tomato paste and hot water, whisking until smooth. Simmer over medium heat 2–4 minutes until the sauce is slightly thickened.
Add the shredded rotisserie chicken to the pan and toss until evenly coated in the sauce; taste and adjust with more salt, pepper, or a pinch of sugar if desired. Squeeze in the lime juice and remove from heat.
If using, divide 1 cup of the shredded cheddar among the bottoms of the stand-up taco shells and broil 1–2 minutes until the cheese melts—watch closely to avoid burning.
Fill each taco shell with the sauced chicken and sprinkle the remaining 1 cup of cheddar on top so it melts from the warm filling. Add desired toppings and serve immediately.