Preheat oven to 425. Combine potatoes, sliced garlic, onions, olive oil, salt and pepper until the veggies are coated.
Put the veggies on a sheet pan and bake for 20-25 minutes.
Move the veggies to the side and add the salmon, peppers, sliced lemon, and oregano. Pour any remaining olive oil from the potatoes on the salmon and top with crushed garlic. Bake 8 minutes.
Add tomatoes, feta cheese, and top everything with the juice of one lemon. Bake 5 more minutes.