Preparation

• In a small bowl, combine the chili powder, cumin, oregano, and 1 tsp. salt. Rub the steak all over with the spice mixture.
• Heat 1 Tbs. of the oil in a large nonstick skillet over medium-high heat, or alternatively, heat an oiled grill to medium high (400°F to 475°F). Cook the steak, flipping once, until rare, 4 to 5 minutes. Transfer to a cutting board. Let rest 5 minutes, then thinly slice across the grain.
• Return the pan to the heat, and add more oil if dry. Add the onion, bell pepper, and garlic to the pan, season generously with salt, and cook, stirring occasionally, until the onion is softened and the peppers are crisp-tender, about 5 minutes. Transfer to a bowl; set aside. Wipe out the skillet with paper towels; set aside.
• Put the tortillas on a work surface. Sprinkle 1/3 cup of the cheese over half of each tortilla. Evenly divide the steak and vegetables over the cheese. Sprinkle the remaining 2 cups cheese over the steak and vegetables. Fold each tortilla in half so that the empty side covers the filling.
• Heat 1 tsp. of the oil in the skillet over medium heat until shimmering. Add 2 of the quesadillas, and cook until golden-brown and the cheese is melted, about 3 minutes per side. Transfer to a clean cutting board, and then repeat with the remaining oil and quesadillas in 2 more batches. Cut the quesadillas into wedges, and serve with the salsa, guacamole, sour cream, and hot sauce.