Preheat the oven to 400 degrees Fahrenheit (205 degrees Celsius).
Prepare the muffin tin by spraying each well liberally with olive oil spray OR add ½ teaspoon olive oil into each well and evenly distribute the oil in each muffin well. Set aside.
Whisk the milk, vinegar, egg, and minced onion in a medium-sized bowl. Set aside for 5 minutes.
Whisk the flour, salt, pepper, sugar, baking powder, baking soda, garlic powder, rosemary, and Parmesan cheese in a large bowl.
Switch to a spatula or wooden spoon and add the wet ingredients into the dry ingredients. Stir to combine, being careful not to over mix the batter.
Use a large cookie scoop (optional) or a ¼ cup measuring cup, evenly scoop the batter into each prepared muffin well. Each muffin well should be no more than ¾'s full. *Note - spraying the cookie scoop or measuring cup with olive oil spray will prevent the batter from sticking to the scoop.
Bake the muffins in a preheated oven for 18 minutes. Remove the muffins from the oven and brush each one lightly with olive oil. Return the muffins back to the oven for an additional 3-5 minutes or until the muffins are golden brown and a toothpick inserted into the center of the muffins come out clean.
Allow the muffins to cool slightly on a wire rack for 5 minutes. If needed run a paring knife around each muffin to loosen from the tin and continue cooling the muffins on a wire rack.
These focaccia muffins are best served warm.
Video
Notes
Store any leftovers in an airtight container in the refrigerator for up to 7 days.Baked focaccia muffins may be frozen.Store in an airtight freezer container and freeze for up to 2 months.