Combine the first 5 ingredients in a small bowl; sprinkle the spice mixture evenly over both sides of tuna.
Heat a grill pan over high heat. Coat pan with cooking spray. Add tuna; cook 2 minutes on each side or until medium-rare or until desired degree of doneness. Cut tuna into 1/4-inch-thick slices.
Warm tortillas according to package directions. Divide tuna evenly among tortillas; top each with 2 tablespoons avocado, 1 tablespoon onion, 1 1/2 teaspoons cilantro, and 3 jalapeño slices. Top each with 1 teaspoon sour cream. Serve tacos with lime wedges.
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