Make tortilla chips: In a deep-fryer heat oil over medium-high heat. When hot, add tortilla strips and fry until crisp and golden, about 1 minute. Remove strips from oil with a slotted spoon, drain on paper towels and sprinkle evenly with salt.
Make guacamole: In a bowl combine all guacamole ingredients and mash together with a fork or potato masher until blended but still chunky. Season to taste with salt, pepper and Southwest seasoning. Cover tightly by laying a sheet of plastic wrap directly on surface of guacamole and gently squeezing out any air bubbles. Refrigerate until ready to use.
Make salsa cruda: In a bowl combine all salsa cruda ingredients, stirring until well-mixed; season to taste with salt and pepper. Cover and refrigerate until ready to use.
Make tuna: Heat a stovetop grill or cast-iron skillet until nearly smoking. Season tuna steaks with salt and pepper and sear, about 3 minutes per side, until crusty and browned. For rare, serve immediately; for medium, reduce heat and continue cooking another 3 minutes. To serve, place tuna steaks and tortilla chips on 2 plates, and spoon guacamole and salsa cruda alongside. Garnish decoratively with sour cream and cilantro sprigs.
Yield: 2 servings