Thinly slice the English cucumber into rounds and place them in a medium mixing bowl.
In a small jar, whisk together the rice vinegar, honey, fresh dill, and lemon zest until the honey is fully dissolved.
Pour the dressing over the cucumbers, toss to coat, and sprinkle with toasted sesame seeds; set aside to marinate while you cook the fish.
Pat the salmon fillet dry with paper towels to ensure a good sear and season both sides evenly with sea salt and black pepper.
Heat the avocado oil in a non-stick skillet over medium-high heat until the oil is shimmering but not smoking.
Place the salmon in the pan, skin-side down, and sear for 4 to 5 minutes without moving it until the skin is exceptionally crispy.
Carefully flip the fillet and cook for an additional 2 to 3 minutes until the salmon is just opaque in the center and flakes easily.
Plate the warm salmon immediately alongside the chilled, zesty cucumber salad for a bright contrast in temperatures.