Review all recipe notes and instructions before beginning.
In a bowl, whisk together the olive oil, lime juice, jalapeños, adobo, garlic, brown sugar, salt, cumin, and chili powder.
Pour marinade into a large sealable bag and add steak. Marinade for at least 2 hours or overnight.
Heat olive oil in a cast iron skillet over high heat. Sear the skirt steak for 2-4 minutes per side depending on thickness (for medium to medium rare).
Remove from heat and rest on a cutting board for 5 minutes. Repeat if needed with the other half of the steak.
Preheat the oven to 450 degrees. Mix the butter and spices in a small bowl. Set aside.
Slice the skirt steak thinly against the grain.
On a large baking sheet, assemble the quesadillas. Gently fold each tortilla in half. Sprinkle ¼ cup of cheese inside each tortilla. Divide sliced carne asada between the 6 tortillas. Sprinkle another ¼ cheese on top of the meat. Brush the top of each with the butter.
Bake for 8-10 minutes or until golden. Cut in half.