01 - Combine tuna cubes with soy sauce, sesame oil, lime juice, and chili flakes in a bowl. Let marinate while preparing remaining toppings.
02 - Whisk together sour cream, lime juice, and chopped pickled jalapeños until smooth. Season with salt and pepper to taste. Set aside.
03 - Preheat a skillet over medium-high heat. Sear marinated tuna for 30-60 seconds per side, keeping the center rare. For poke-style preparation, skip searing and serve raw.
04 - Arrange tortilla chips on a serving platter or ovenproof tray. Sprinkle shredded cheese evenly over chips. Broil for 1-2 minutes until melted, if desired.
05 - Layer seared tuna over the cheesy chips. Top with diced avocado, quartered tomatoes, red onion, jalapeño slices, and fresh cilantro.
06 - Drizzle jalapeño-lime crema generously over the assembled nachos. Serve immediately while chips remain crispy and toppings are fresh.