In a small bowl, whisk together chili powder, cumin, paprika, coriander, cayenne pepper, and salt to taste (I like ½ teaspoon), Whisk in cornstarch if desired. (Or, substitute one packet store-bought taco seasoning).
In a large skillet over medium-high heat, heat oil until shimmering. Add onion and cook until softened, about 5 minutes. Stir in taco seasoning, garlic, and oregano until fragrant, about 30 seconds.
Add ground turkey and cook, stirring occasionally, until almost cooked through but still slightly pink, about 2 minutes.
Stir in tomato sauce, vinegar, and brown sugar. Bring to a simmer and cook until thickened, about 4 minutes. Season to taste with salt and pepper.
Serve the meat hot with the tortillas and all your favorite toppings like lettuce, tomatoes, sour cream, cheese, and diced avocado.