1-First Step: Mix the chimichurri sauce In a small bowl, combine 1/2 cup olive oil, 1/4 cup red wine vinegar, 1 tablespoon lemon juice, 1/2 cup minced curly leaf parsley, 1 tablespoon dried oregano, 1/2 teaspoon red pepper flakes, 1/2 teaspoon salt, and 1/2 teaspoon black pepper. Stir well until the mixture looks evenly blended. Let it sit while you cook the steak so the herbs can soften and the flavors can come together.

2-Second Step: Prep the steak and onions Pat the 1 pound flank steak dry with paper towels, then slice it into thin strips if it is not already sliced. This helps it cook quickly and stay tender. Slice the 2 large onions so they cook evenly and become soft and sweet in the skillet.

3-Third Step: Cook the steak Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the steak strips in a single layer and cook for about 2 to 4 minutes, stirring once or twice, until browned and just cooked through. Avoid overcrowding the pan, since that can cause the steak to steam instead of sear. Remove the steak to a plate and let it rest for a few minutes.

4-Fourth Step: Cook the onions In the same skillet, add the sliced onions. Cook over medium heat for 5 to 7 minutes, stirring often, until they turn soft, golden, and lightly caramelized. If the pan looks dry, add a tiny splash of oil or a spoonful of water to keep them from sticking. The onions should taste sweet and savory, which pairs perfectly with the tangy chimichurri.

5-Fifth Step: Combine the filling Return the steak to the skillet with the onions and spoon in some of the chimichurri sauce. Toss everything together just enough to coat the meat lightly. You want the steak juicy, not drenched. Save extra sauce for serving so the flavor stays bright and fresh.

6-Sixth Step: Build the quesadillas Lay out the 4 flatbreads on a clean surface. Sprinkle 2 cups shredded Monterey Jack cheese evenly over half of each flatbread. Add the steak and onion mixture on top of the cheese, then fold the flatbreads over to close. Press gently so the filling stays in place.

7-Seventh Step: Toast until crisp Wipe the skillet if needed and place it over medium heat. Cook each folded quesadilla for 2 to 3 minutes per side, or until the bread is golden brown and the cheese is fully melted. If your pan is very hot, lower the heat a little so the outside does not burn before the cheese melts. A good quesadilla should sound lightly crisp when you lift it from the pan.

8-Final Step: Slice and serve Transfer the quesadillas to a cutting board and let them rest for 1 minute before slicing. This short rest helps the cheese settle so the filling does not slide out. Cut each one into wedges and serve with the remaining chimichurri sauce on the side. If you want to make the dish even richer, add mashed avocado or a spoonful of avocado chimichurri on top.