In a small bowl, combine the ground cumin, paprika, chili powder, onion powder, garlic powder, and chicken bouillon powder; add salt and pepper to taste (suggest starting with 1/2 teaspoon each) and set aside.
Heat the olive oil in a large nonstick pan over medium-high heat. Add the minced garlic and cook about 30 seconds until fragrant.
Add the reserved spice mixture to the pan and cook, stirring, for 1 minute.
Stir in the tomato paste and hot water, mixing until smooth. Simmer over medium heat 2–4 minutes until slightly thickened.
Add the shredded rotisserie chicken to the sauce and toss until evenly coated; taste and adjust seasoning with more salt, pepper, or the optional teaspoon of sugar. 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 melted, watching closely.
Fill each shell with the warm chicken mixture, then sprinkle the remaining 1 cup of Cheddar on top to melt from the heat.
Add desired toppings and serve immediately.
