Preheat oven to 400 degrees Fahrenheit and lightly grease a 9x13 inch baking dish with cooking spray.
Heat olive oil in a large skillet over medium-high heat. Add diced onion and sauté for 4 minutes until translucent.
Incorporate ground turkey and minced garlic, cooking until the meat is browned and internal temperature reaches 165 degrees Fahrenheit.
Stir in chili powder, cumin, smoked paprika, salt, pepper, and tomato sauce. Simmer for 5 minutes until the sauce thickens and coats the meat.
Arrange taco shells upright in the prepared baking dish, packing them tightly to keep them standing.
Distribute the turkey mixture evenly among the shells and top each with shredded cheese.
Bake for 10 to 12 minutes until the cheese is fully melted and the edges of the shells are crisp.
While baking, combine avocado, Greek yogurt, lime juice, and cilantro in a food processor or blender. Process until a smooth emulsion is formed.
Remove tacos from the oven and top with the avocado sauce before serving.