Preheat the oven to 450°F and line a large baking sheet with a silicone liner or parchment; spray with olive oil if using parchment.
In a medium bowl whisk together the flour, baking powder, and kosher salt until evenly combined.
Add the drained non-fat Greek yogurt and mix with a fork or spatula until the mixture forms small crumbles and comes together into a dough.
Lightly flour a work surface and turn the dough out; knead a few times (about 20 turns) until tacky but not sticky.
Divide the dough into 4 equal portions (about 3 to 3-3/8 oz each) and roll each into a ball.
Using a floured rolling pin, roll each ball into a thin oval about 7 to 8 inches across and place on the prepared baking sheet.
Lightly spritz each dough oval with olive oil and sprinkle Everything Bagel Seasoning in a 1-inch border around the edge, leaving the center plain.
Toss half of the sliced red onion with 1 tablespoon olive oil and distribute the onion evenly in the center of each flatbread.
Bake in the preheated oven 10 to 14 minutes until the crust is golden and crisp.
Remove the flatbreads from the oven and dollop the cream cheese in the center of each, keeping the seasoned edges clear.
Top each with tomato slices, then smoked salmon, then sprinkle with drained capers and garnish with fresh dill.
Optional air-fryer method: preheat the air fryer to 400°F and cook each rolled dough (in the basket) until firm and golden, about 5 to 6 minutes, turning once halfway; repeat with remaining dough.
