1. In a medium-size bowl, combine the flour with the baking powder and salt. Then add in the yogurt and mix the dough using a fork, your hands, or a rubber spatula until the dough is wet but still slightly crumbly with large doughy pieces. 
2. Then turn the dough out onto a well-floured surface and use your hands to knead it into a smooth ball of dough. Separate the dough into 4 equal pieces. 
3. Roll each piece of dough into a 5-6 inch long, 3/4 inch wide log and form into a circle and pinch the ends of the dough together with your fingers. 
4. In a small bowl combine the egg yolk with some water and brush the egg wash all over each bagel on the top and the middle. Then leave plain or add your toppings, if desired. 
5. Preheat the air fryer to 350 degrees F and spray the air fryer basket with olive oil spray. Place the formed bagels into the air fryer in a single layer about 2 inches apart. Close and cook for about 10 minutes until they are nice and golden and cooked through. Note: check the bagels at around 8-9 minutes to make sure they do not get too golden brown since air fryers vary. 
6. Remove the bagels from the air fryer and let them cool for 5-10 minutes before slicing and topping them. 

To make gluten-free bagels

1. In a medium-size bowl, combine the gluten-free all-purpose flour with the baking powder and salt. Then add in the yogurt and egg white and mix the dough using a fork, your hands, or a rubber spatula until the dough is wet but still slightly crumbly with large doughy pieces. 
2. Then follow the rest of the recipe as explained above.