1. Heat oven to 350°.
2. Heat oil in a large skillet over medium heat. Add onion and cook until golden. Add tomato paste, garlic, chili powder, paprika, coriander, and cayenne pepper. Cook, stirring, until tomato paste has darkened and spices are toasted, about 2 minutes. Add water and scrape up bits from bottom of pan. Add crab and gently stir to combine and heat through. Add lime juice and season with salt and pepper.
3. Place a layer of tortilla chips on bottom of an oven-safe serving platter. Top with half the cheese and half crab mixture. Top with another layer of chips, remaining cheese, and remaining crab mixture. Transfer to oven until cheese is melted, about 5 minutes.
4. Remove from oven, top with cilantro and onion. Serve immediately with salsa, guacamole, and sour cream on the side.