Add the avocado oil to a preheated skillet over medium-high heat.

Season the salmon with the salt, pepper, and Italian seasoning.

Place the salmon skin down in the pan. Let cook for 4-5 minutes, or until the skin is lightly browned and starting to crisp.

Flip and cook for another 4-5 minutes on the other side. Make sure there is plenty of oil under the salmon so it doesn't stick. I prefer to use a stainless steel skillet for this recipe, but a non-stick pan also works.

While the salmon cooks, melt the butter in a separate pan over medium heat. Add the diced onion and let cook for 4-5 minutes, or until soft and translucent. Add the garlic and cook for 1 minute.

Whisk in the flour until no lumps remain. Turn the heat down to medium-low and continue to cook, whisking continuously, for another 2-3 minutes. Add the rest of the sauce ingredients to the pan and stir to combine. Bring back up to a light simmer, and let cook for several minutes.

When the salmon is done, pour the sauce over the top and serve hot.