Preheat oven to 400 degrees F. Line a muffin pan with 6-8 paper cups or you can grease the muffin pan with some shortening.
In a large bowl, whisk together the flour, baking powder, yeast and salt. Set aside
In another bowl, using a hand held electric mixer, whip eggs. With mixer on medium, mix in the oil, vanilla, milk and orange zest. Mix in the sugar.
With the mixer on low/medium speed, gradually mix in the flour(dry ingredients). Do not over mix. Let the batter stand for 10 minutes.
Preheat oven to 400 degrees F. Divide the batter into prepared paper cups or greased pan. If adding the candied orange pieces, add a few to each mantecada. Bake for 20 to 25 minutes or until a toothpick comes out clean from the center and mantecadas are golden brown. Remove from oven and let cool. Sprinkle with granulated sugar while they are still warm.