Pat salmon dry with a paper towel, place on a baking sheet. Drizzle with olive oil, then season with onion salt and black pepper. Bake for 20 minutes. Set aside to cool.

Place Greek yogurt into a small mixing bowl. Add lemon zest, fresh lemon juice, and finely chopped dill. Stir to combine, then taste and adjust seasoning as needed.

Use a sharp knife to thinly slice the cucumber on a diagonal about ¼" thick. You don't want them too thin, or they won't be able to hold the weight of the yogurt sauce and salmon.

Garnish with fresh dill, drained capers, or everything bagel seasoning blend. For the stacks with only fresh dill or capers, sprinkle a tiny pinch of flaky sea salt on top. Serve immediately!