In the bowl of a stand mixer, stir together masa flour, salt, chili powder, and baking powder. Add vegetable oil and chicken broth, and mix on low until combined. Use mixer on medium speed to mix dough for approximately 10 minutes. This beats air into the dough to give it a lighter texture. If you do not have a mixer, stir it as long as you can by hand, and then let the dough rest for at least 10 minutes.