Heat 2 tablespoons of vegetable oil in a pot over medium heat, add the chopped onions and fry until golden. Increase heat to medium-high; add the ground beef and brown until no longer pink, stirring occasionally. Drain well and return to the skillet if needed.
Add the taco seasoning, turmeric, crushed tomatoes, 3/4 cup of salsa sauce and green onion. Cook uncovered over medium-low heat for 10-15 minutes, stirring occasionally. Then add the refried beans and oregano. Mix well and cook for 5 more minutes. Taste and adjust seasonings.
Preheat the oven to 390 degrees F. Place the taco shells into baking dish, standing up.
Fill the taco shells with beef mixture. Spoon a tablespoon of salsa sauce over the fillings.
Sprinkle with cheese.
Place on the middle rack of the oven and bake until heated through and cheese is melted.