Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a food processor, add the salmon fillet and pulse until finely chopped but not pureed. Transfer to a large bowl.
Add breadcrumbs, Parmesan cheese, parsley, minced garlic, lemon zest, salt, pepper, and the egg to the bowl with the salmon. Mix until well combined.
Using your hands, form the mixture into meatballs, about 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 15-20 minutes, or until cooked through and golden brown.
While the meatballs are baking, prepare the creamy avocado sauce. In a bowl, mash the avocado and then mix in Greek yogurt, lemon juice, minced garlic, salt, and pepper until smooth.
Once the meatballs are done, serve them warm with the creamy avocado sauce drizzled on top or on the side for dipping.