Season skirt steak with olive oil, salt, pepper, chili powder, and cumin.
Cook on high heat for roughly 3 minutes each side, for medium-rare.
Let the steak rest for 10 minutes.
While the steak is resting, sauté onion and garlic until slightly translucent. Add bell peppers, jalapeño, salt, and pepper, cook slightly.
Slice the steak into strips.
Mix the steak into the pepper mix. Remove from heat and set aside.
In a clean pan, melt butter. Lay the tortilla on the buttered pan, add cheese, fajita mixture, more cheese, then top with another tortilla and pat it down.
Flip the quesadilla over and cook the other side until it’s golden.
Remove from pan and cut into quarters or eighths. Repeat these steps with the remaining tortillas.
Serve immediately with a dollop of Greek yogurt, salsa, and guacamole.