Preheat oven to 375F. Move the rack to the middle position. Line a baking sheet with foil. Wrap the tortillas in foil and put them in the oven right away.
Place a piece of salmon on the baking sheet and coat it with olive oil. Gently sprinkle with garlic powder, ground cumin, chili powder, and salt & pepper. Cook in oven for 10-15 minutes or until it flakes easily with a fork.
Meanwhile, combine the sauce ingredients. Set aside. Prepare the avocado and lettuce.
When the salmon is done, roughly cut it into bite-size pieces using a fork. Assemble tacos immediately. Serve with extra lime if desired.
If you're feeding 4+ people, I suggest buying a large piece of salmon or 2-3 smaller ones.