In a bowl, toss the sliced chicken with olive oil and spices. Do this at room temp, around 70°F, and take about 1 to 2 minutes to really coat everything. Use your hands or tongs and fold the strips over each other so the spices stick evenly. You’re looking for a glossy, deep red coating and no pale spots left. The chicken should feel lightly slick but not dripping. If you rush this, the seasoning won’t stick and the flavor ends up patchy.

Heat a skillet over medium-high, about 7 out of 10, for 2 minutes before adding the chicken, onion, and pepper. Spread everything into a single layer and let it cook undisturbed for 3 minutes, then stir and cook another 5 to 7 minutes. Stir with a scraping motion to pick up browned bits. You’ll see the chicken turn opaque and the veggies soften with slight char at the edges. You’ll smell a toasty, savory aroma. Go past 10 minutes and the chicken dries out and the peppers lose their bite. (I used to stir too often and never got that browning. Let it sit.)

Lay tortillas flat on the counter and work quickly while the filling is still warm, around 140°F. Sprinkle cheese on one half, add the filling, then another light layer of cheese. This takes about 2 minutes total for all tortillas. Use a gentle scoop and drop motion so the filling stays evenly spread. You should see some cheese peeking out at the edges. Skip that second layer of cheese and the quesadilla won’t hold together when cut.

Heat a pan over medium, about 5 out of 10, and melt a little butter. Cook each quesadilla for 3 to 4 minutes per side. Press lightly with a spatula once at minute 2 to help it crisp evenly. You’re watching for a deep golden surface with darker spots and melted cheese inside. You’ll hear a faint sizzle and smell toasted butter. Flip too early and it won’t crisp. Leave it too long and the tortilla burns before the cheese fully melts.

Let the quesadillas rest for 1 minute off heat so the cheese settles to about 150°F. Then slice into wedges using a firm downward press with a knife. You should see melted cheese stretching slightly and the filling holding in place. Sprinkle cilantro right after slicing so it sticks slightly to the warm surface. Cut too soon and the filling spills. Wait too long and the cheese firms up too much.