Preheat the oven to 425 degrees.
Beat eggs and add sugar.
Mix until well combined.
Add the milk and mix again.
Slowly drizzle in the oil while mixing.
Add vanilla and orange zest (if using).
In a large bowl, combine the flour, salt, baking powder, and cinnamon.
Add the dry ingredients a bit at a time.
Occasionally scrape down the sides until the flour mixture is completely mixed.
Line a muffin pan with cupcake wrappers.
Pour 3/4 of the mixture to each of the wrappers.
Once the oven is ready, place the muffin pan inside the oven.
Immediately lower the oven to 400 degrees F.
Bake for 15 minutes, or until a toothpick comes out clean.