Slice the flank steak into thin, bite-sized strips and toss in a bowl with the ground cumin, garlic powder, sea salt, and black pepper.
Heat the extra virgin olive oil in a large non-stick skillet over medium-high heat.
Add the thinly sliced red bell pepper and red onion to the skillet, sautéing for 3-4 minutes until they are tender and slightly charred.
Push the vegetables to the side and add the seasoned steak strips to the pan, searing for 2-3 minutes until browned and cooked to your desired level of doneness.
Remove the steak and vegetables from the skillet and set them aside on a plate.
Wipe the skillet clean and place the tortilla in the center over medium heat.
Sprinkle the mozzarella cheese over one half of the tortilla, then layer the steak and sautéed vegetables on top of the cheese.
Fold the tortilla in half and press down with a spatula, cooking for 2 minutes per side until the exterior is golden brown and the cheese is fully melted.
While the quesadilla toasts, mash the avocado in a small bowl with the lime juice and fresh cilantro to create a quick guacamole.
Slice the quesadilla into wedges and serve immediately with the fresh guacamole on the side.