Mix your blackening seasoning ingredients together in a medium bowl.
Heat a griddle on high heat and drizzle with oil.
Brush the salmon with butter so the seasoning sticks better. Rub each side with blackening seasoning, lay on the griddle, and cook until beautiful char
marks have formed on each side and the salmon is no longer sticking to the griddle (which means it's ready to flip). Make sure not to overcook salmon.
In the meantime make the aioli by coming everything but the oil into a small or medium food processor. Pulse the mixture to break up the garlic and egg.
Then slowly stream in the oil while the processor is running until a homogeneous mixture forms. Stir in the herbs and taste for salt.
Assemble the sandwiches: spread a nice spoonful of the aioli onto the bottom of the bun, place on a piece of salmon, lettuce, tomato, onion slices,
and spoon more aioli on the top bun and close. Enjoy!