Preheat the oven to 375°F (190°C).
Prepare a baking dish by lightly greasing it with olive oil.
Season the salmon fillets with salt, pepper, and garlic powder on both sides.
Place the salmon fillets skin-side down in the prepared baking dish.
In a bowl, mash the avocados and mix in lemon juice, salt, and pepper.
Spread the avocado mixture evenly over each salmon fillet, then sprinkle with crumbled feta on top.
Drizzle the remaining olive oil over the top.
Bake for 20-25 minutes or until the salmon flakes easily with a fork.
Remove from the oven and garnish with fresh herbs before serving.