Preheat the oven to 375°F (190°C) and position a rack in the middle; line a baking sheet with foil.
Place the salmon on the prepared baking sheet and brush or rub with the olive oil.
Season the salmon with garlic powder, chili powder, ground cumin, and salt and pepper to taste.
Bake the salmon for 10–15 minutes, until it flakes easily with a fork.
While the salmon bakes, combine the Greek yogurt, lime juice, minced garlic, chopped cilantro, and a little salt and pepper in a medium bowl; taste and adjust seasoning.
Prepare the toppings: dice the avocado and shred the iceberg lettuce.
When the salmon is done, use a fork to flake or roughly break it into bite-size pieces.
Assemble tacos by placing salmon in warm tortillas, topping with yogurt sauce, avocado, and shredded lettuce; serve with lime wedges.