Combine together all the seasoning ingredients and rub generously on the salmon until it is completely covered.
Heat olive oil in the skillet.
Place the seasoned salmon and cook until lightly browned and crisp, about 5 minutes. Flip and cooked the other side, another 5 minutes.
Take off the heat and set aside.
In a bowl mix together the mayonnaise, garlic, salt and pepper and finish with the lemon juice. Mix well and set aside.
Toast the insides of the buns and set aside.
Now it is time to assemble the sandwich. Spread a thick layer of the garlic aioli on the bottom bun. Add a few arugula leaves to it. Now add your salmon filet. Then add a slice of onion, one slice of tomato and a few slices of avocado. Add another generous spread of the garlic aioli to the top bun.