In a medium bowl, combine all the relish ingredients and toss gently. Reserve.

Using a long knife, cut tuna steak into triangle shaped strips, 1 1/4" per side.

In a small bowl combine spices, and rub spice mixture onto three long sides of the tuna.

Heat a nonstick skillet over high heat. When pan is smoking hot, add canola oil. Wait 10 seconds, then add tuna. Sear for 30 seconds per side, or until fish is cooked on the outside, but still rare on the inside. Transfer strips to a cutting board, and slice into 1/2" thick triangles.

To assemble, line up tortilla chips. Top each with a dollop of avocado relish and a slice of tuna.