Prep the toppings: Slice onion, tomato, and cucumber very thin. Chop dill or chives.
Rinse and dry the capers.
Toast the bagel: Toast until golden and crisp on the cut sides. For extra flavor, swipe a tiny bit of butter on the hot surface.
Spread the cream cheese: Be generous—edge to edge. The cream cheese acts as a barrier and keeps the bagel from getting soggy.
Add the salmon: Fold slices of smoked salmon over the cream cheese so you get layers in every bite.
Layer the veggies: Add tomato, cucumber, and red onion.
Keep it even so the bagel doesn’t tip or slide apart.
Season: Sprinkle capers, fresh dill or chives, and a few grinds of black pepper. Add a light squeeze of lemon and a tiny drizzle of olive oil if you like.
Finish and serve: Top with the other bagel half, press gently, and cut in half for easier eating.