Preheat your Blackstone grill to medium-high heat, aiming for a temperature around 400°F.

Prepare the grill by adding vegetable oil and spreading it evenly.

Cook diced skirt steak and sliced onions on the grill, seasoning with onion powder, salt, and black pepper for about 4–8 minutes.

Shift the cooked steak and onions to one side of the grill and lower the heat to medium.

Arrange the tortillas on the cleared space of the grill, sprinkle cheese, add steak and onion mixture, and top with more cheese.

Fold the tortillas in half and grill for 1–2 minutes on each side until golden brown.

Slice the quesadillas into wedges and serve with salsa, guacamole, or sour cream.