In a bowl, combine salmon, onion, lemon juice, cumin, ginger, hot sauce, and chili flakes; mix well. Cover; chill 10 minutes. Meanwhile, shred lettuce and core and chop tomatoes; cover and chill separately until serving time.
Heat a 12-inch nonstick frying pan over medium-high heat. When hot, add salmon mixture. Cook, stirring often, until fish is just opaque but still moist-looking in center, about 6 minutes.
Serve immediately. To eat, wrap salmon mixture in tortillas; add lettuce, tomatoes, and sour cream to taste.