Preheat oven to 350 degrees F.
While the oven is preheating, make the sauce by combining the yogurt, avocado, lemon, garlic, and dill in a mini food processor or blender. Add water, 1 tablespoon at a time if too thick. Season to taste with salt and pepper and additional lemon or garlic.
Line a rimmed baking sheet with parchment paper and grease with 2 teaspoons of oil.
Season both sides of the salmon with salt and place on the parchment paper. Note: you can leave the salmon as a whole fillet or cut into portion-sized pieces--it will cook a little faster if cut, but in my opinion, it's easier to just leave it whole.
If desired, add additional veggies to the sheet pan. If they will need the same amount of time to cook, include them for the whole cooking time--as I did with the sliced fennel and zucchini in the photos. If they need less time, add them later in the cooking process--as I did with the frozen baby peas in the photos. (See recipe notes for more tips.)
Bake fish for 20-25 minutes, depending on size and thickness. Drizzle the sauce on top and serve or let everyone take their own sauce (recommended for family-style dinners). Enjoy!