In a skillet, sauté eggplant in oil over medium heat until the eggplant is shrunken and softened, about four to five minutes.

Add stock, garlic, tahini, lemon juice, salt, red pepper flakes, and black pepper. Cover and reduce heat to medium–low. Simmer for 20 minutes.

Cool for several minutes, then puree with immersion blender until smooth.

Preheat oven to 350 degrees Fahrenheit.

In a food processor, place the pistachios, oil, fried onions, basil, sage powder, onion powder, and garlic powder. Pulse five to six times until the mixture has a grainy consistency. Set aside.

Rinse the fish and pat dry. Sprinkle with the salt, black pepper, and lemon juice. In a large nonstick skillet sprayed with nonstick cooking spray, pan-sear the fish on both sides to seal in the juices, about two minutes per side. Transfer the salmon to a baking pan and allow to cool for several minutes.

Spread the mayonnaise on the salmon, then pat the pistachio mixture evenly on top. The layer of pistachio mixture should be thick. Bake in the oven for 20 to 25 minutes.

Serve warm or at room temperature with the eggplant puree, if desired.