**Prepare the Steak**:
- Season the steak with salt, pepper, garlic powder, and onion powder.
- Preheat your grill to 400°F. Grill the steak for 3 minutes on each side, or until cooked to your preferred doneness.
- Let the steak rest for 5-6 minutes, then slice it thinly against the grain.
**Make the Chipotle Lime Mayo**:
- In a mixing bowl, combine mayonnaise, sour cream, pickled jalapeño brine, chipotle paste, and lime juice.
- Whisk until smooth and set aside.
**Assemble the Quesadillas**:
- Lay the tortillas flat. Spread the shredded Mexican cheese blend and pepper jack cheese evenly on each tortilla.
- Layer the sliced steak on top of the cheese, followed by fresh cilantro, diced onions, and sliced jalapeños.
- Close the tortillas in half to form a half-moon shape.
**Cook the Quesadillas**:
- Heat a skillet or griddle over medium-high heat. Lightly grease it with olive oil.
- Cook the quesadillas for 1-2 minutes per side until the tortillas are crispy and golden brown, and the cheese is fully melted.
**Serve**:
- Slice the quesadillas into wedges and serve immediately with a drizzle of Chipotle Lime Mayo. Garnish with fresh cilantro and diced red onions.