Heat grapeseed oil in a large pan until shimmering. Add chopped onions. Saute until lightly browned. Add crumbled ground turkey, ground beef, and salt. Cook until fully browned. Remove from heat.
Drain excess oil from meat/onion mixture (blot with towels if easier). Preheat oven to 400 °F (205 °C).
Combine taco seasoning and meat mixture. Simmer for 10 minutes, stirring occasionally.
While meat is simmering, on one baking sheet, evenly space the taco shells. On another baking sheet, spread out flour tortillas and sprinkle with cheese (you may need to do this a second time). Place tortilla on bottom rack and shells on top rack. Warm in oven until cheese is melted approximately 5 minutes.
Put the cheesy tortillas carefully around the outside of the taco shell. Fill with whatever toppings you want.
There are 688 calories in 1 serving of Taco Tuesday.