01 - Combine tuna cubes with soy sauce, sesame oil, lime juice, and chili flakes in a bowl. Let marinate while preparing remaining components.
02 - Whisk together sour cream, lime juice, and chopped pickled jalapeños until smooth. Season with salt and pepper to taste. Set aside for serving.
03 - Preheat skillet over medium-high heat. Sear marinated tuna for 30-60 seconds per side, leaving center rare. For poke-style preparation, skip cooking and serve raw.
04 - Arrange tortilla chips on 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 cheese-topped chips. Add diced avocado, quartered tomatoes, red onion, jalapeño slices, and fresh cilantro.
06 - Drizzle jalapeño-lime crema generously over assembled nachos. Serve immediately while chips remain crisp and toppings are fresh.