Add all the dressing ingredients, except the olive oil and garlic, into a jar and whisk together until smooth. Add the oil and garlic. Put the lid on and shake the jar until it forms a creamy sauce.
Place the salmon on a plate. Pat both sides dry. Lightly sprinkle salt onto both sides. Let sit for 5 minutes.
While the salmon is marinating, combine the arugula, tomatoes, and cucumbers in a big salad bowl.
Heat a skillet (large enough to fit both pieces of salmon) with the oil over medium-high heat. Swirl the pan to coat the bottom of the pan with oil. Once the oil is hot, add the salmon, skin-side down. Let cook, undisturbed for 4 to 6 minutes, or until the bottom turns golden brown. Once the skins are fully crisped up, flip them over and turn the heat down to medium. Cook for another 4 to 6 minutes, to your desired doneness. To check the doneness, use a fork or paring knife to probe the thickest part of the salmon. It should flake easily and the middle should turn pale pink. Remove the cooked salmon from the pan and set it aside on a separate plate (leaving it skin-side up so it doesn’t become soggy).
Add 2 tablespoons of dressing over the salad and toss to coat.
Serve the salmon hot: Separate the salad onto two serving plates. Place the salmon to the side of each salad (if placed on top while hot it will wilt the leaves).
Serve the salad cold: Alternatively, you can also wait until the salmon cools off a bit, and top it on the big bowl of salad to serve it family style.
Serve with the extra dressing on the side and enjoy as a main dish.