In a small bowl, mix together the spices for the fajita veggies. Toss this with the sliced peppers and onions. Set aside.
Heat a large griddle or large cast iron skillet over medium-high heat. Lightly oil the surface. Working in batches as needed, cook the marinated steak for 3-5 minutes per side or until desired doneness (Medium Rare: 130-135°F; Medium: 135-145°F; Well: 145-155°F). Cook the fajita veggies for about 5-7 minutes, until the onions are soft but the peppers still have a slight bite to them. Remove steak and veggies to plates when done.
If necessary, wipe down the surface of your griddle with a paper towel in preparation for toasting the quesadillas.
To assemble the quesadillas, thinly slice the cooked steak against the grain.
Cover one half of a tortilla with as much of the shredded cheese as you like. Top with your desired amount of sliced steak and fajita veggies, followed by more cheese. Fold the tortilla over the fillings.
Place each quesadilla on the griddle. Cook for 2-3 minutes on each side, until toasted and the cheese is melted.
To make the sauce, mix sour cream with as much of the vinaigrette as desired. Slice the quesadillas and dip into the sauce.
Notes
We love using our Blackstone griddle to make these quesadillas from start to finish, but you can use a stovetop griddle, electric griddle, or a very large cast iron skillet. Feel free to use a packet of your favorite fajita seasoning in place of the listed spices for the vegetables.If you can find a mix of shredded Mexican cheeses, feel free to use those in place of the monterey jack and/or queso blanco.Chipotle says that they use Daisy sour cream in their restaurants, but that they beat it before serving to thin it out and mimic the texture of Mexican crema. If you prefer the thinner/runnier texture, you can thin it out with a bit of milk or you can use Mexican crema in place of sour cream.If you prefer chicken to steak, use the same marinade recipe but swap in 2-3 pounds of boneless/skinless chicken breasts or thighs. Cook the marinated chicken for 5-7 minutes per side, or until the internal temperature reads 165°F. Rest the cooked chicken and slice against the grain before assembling the quesadillas as above.