Grate the cucumber on the large holes of a box grater. Transfer to a clean kitchen towel and squeeze firmly over the sink until most of the water is gone — a watery sauce will pool instead of smear.

Add the lemon zest and lemon juice just before serving. Stir once more and taste again. The sauce should be bright, garlicky in the background, and deeply herby. Set aside at room temperature if using within 30 minutes, or refrigerate and bring back to room temp before plating.

Soak the sliced red onion in a small bowl of cold water for 10 minutes, then drain and pat dry. This takes the raw bite off without losing the sharpness.

Combine the cucumber, cherry tomatoes, drained red onion, and kalamata olives in a large bowl. Drizzle with red wine vinegar and olive oil. Sprinkle with dried oregano, a pinch of kosher salt, and a few grinds of black pepper. Toss gently to coat. Taste and adjust — the salad needs to hold its own against both the salmon and the yogurt sauce, so season with confidence.

Set the salad aside. Don't add the feta yet — it goes on at plating, as a slab.

Pat the salmon fillets completely dry with paper towels — both sides, thoroughly. Season generously on both sides with kosher salt and black pepper. Let them sit at room temperature for 15 minutes. Cold fish hitting a hot pan drops the pan temperature and slows the sear.

Heat avocado oil in a large stainless or cast iron skillet over high heat until the oil is shimmering and just beginning to smoke. The pan needs to be properly hot — a pan that isn't will cause the fish to stick and steam rather than sear.

Place the fillets in the pan presentation-side down. Press each fillet gently but firmly for the first 20–30 seconds to ensure full contact with the pan — skinless fillets will try to curl as the proteins contract. Don't move them after that. Cook for 3–4 minutes until a deep golden crust has formed and the flesh has turned opaque about halfway up the side of the fillet.

Add the butter to the pan. It will foam immediately. Flip the fillets carefully, then tilt the pan slightly and use a spoon to continuously baste the top of each fillet with the foaming butter for 60–90 seconds. The salmon is done when it's opaque all the way through and just barely flakes at the thickest point when pressed. Pull it from the pan and rest for 2 minutes before plating.

Spoon a generous amount of yogurt sauce onto each plate and use the back of the spoon to smear it across most of the surface.

Place a salmon fillet crust-side up on the yogurt smear, centered on the plate.

Spoon the Greek salad around and alongside the salmon — let it tumble naturally against the fish. Lay a thick slab of feta over the salad. Drizzle everything lightly with olive oil. Add a lemon wedge and serve immediately.