Preheat the oven to 375ºF. Generously spray a 9x5-inch loaf pan with cooking spray.

In the bowl of an electric mixer fitted with the paddle attachment, combine the flour, baking powder, baking soda, salt, and cream of tartar. Mix on low until fully combined.

Combine the eggs and buttermilk. Add to the flour mixture and mix until it comes together and forms a stiff dough. Transfer to the prepared pan. With a sharp knife, cut a cross about ½-inch deep into the top of the dough. Bake for 45-55 minutes or until browned and the bread sounds hollow when tapped.  Let cool in the pan for 10 minutes then transfer to a wire rack to finish cooling. Cool for at least 2 hours before slicing and serving.