Step 1

Using a food processor or blender, add all of the marinade ingredients; pulse until smooth.

Step 2

Place skirt steak in a large re-sealable bag. Add marinade, turning several times to coat. Refrigerate for 1 hour.

Step 3

Preheat grill to medium-high heat.

Step 4

Remove skirt steak from bag; discard any leftover marinade.

Step 5

Brush olive oil on both sides of the sliced onions.

Step 6

Place steak and onions on grill. Grill for 3-5 minutes per side, or until steak is done to taste.

Step 7

Reduce grill temperature to medium heat.

Step 8

Transfer skirt steak and onions to a large cutting board and let it rest for 5 minutes. Slice skirt steak against the grain into strips. Slice onions into strips.

Step 9

Lay tortillas out and split shredded cheese, sliced onions and steak evenly between tortillas. Fold each tortilla in half.

Step 10

Grill quesadillas for 2-3 minutes per side, or until cheese has fully melted. Cut quesadillas into wedges and serve with salsa and sour cream.