Heat oven to 425 F.
In a small bowl blend black pepper, 1 ½ teaspoons lemon zest, garlic and mayo.
Coat top side of tilapia filets with mayo mixture, using the back of a tablespoon or spatula.
Coarsely grind the sunflower seeds in a food processor, taking care not to grind them too finely. Press sunflower seeds onto the top sides of the fish filets so that they stick and form a crust.
Wash mustard greens and spin in salad spinner to remove as much moisture as possible.
Put the greens in a bowl and sprinkle with avocado oil and salt. Use your hands to combine and make sure the greens are completely coated with oil.
Using a baking sheet, spread mustard greens and top with coated filets. Bake 10-12 minutes, or until fish is firm and sunflower seeds have started to brown.
Transfer to a serving platter, arranging the fish on top of greens. Sprinkle with ½ teaspoon lemon zest. Serve with lemon wedges.