1. Preheat your oven to 450 degrees F and if you are using a pizza stone place it in the oven now. If you are using a pizza pan, slightly grease it and set aside.In a large mixing bowl, whisk together flour, salt and baking powder.
2. Add oil and yolk and stir in with a wooden spoon.Slowly drizzle in the water, stirring constantly.
3. Transfer the dough onto a lightly floured surface and knead few times until it's smooth.
4. Roll it out into a 12 to 13" circle.
5. Place the flatbread on your prepared pizza pan or the preheated pizza stone (be careful not to burn your hands).
6. Bake for 20 to 23 minutes or until the edges are golden brown and the top has browned spots.
7. Remove from the oven.
8. Let cool while you prepare the filling.
9. Place all ingredients in a medium mixing bowl and mix well until smooth.
10. Spread on baked flatbread.Top with sliced cucumber.Slice the flatbread and serve immediately.