Tempura is not a kind of flour. It is a flour mixture, usually of all purpose, bleached white flour and cornstarch. Tempura mix can be purchased in many Asian markets, and in the ethnic area of many grocery stores. This link = Tempura | Tempura Recipe | Easy Asian Recipes at RasaMalaysia.com
closely resembles my own recipe. The tempura comes out very light, airy, and crispy.
Other recipes use seltzer water in place of a leavening agent, such as baking powder.
I only mention this for those who don't have access to commercially made tempura batter. And in my recipe, I use half wheat flour, and half cornstarch.
Seeeeeya; Chief Longwind of the North