I found it on the internet ages ago and wrote it into my cookery notebook so I sadly do not have the source any more but as I have made some changes I am going to claim credit!
1 cup buttermilk
1/2 cup sugar (original recipe is 3/4 cup)
1 teaspoon vanilla
1 orange zested and juiced
2 cups flour
2 teaspoons baking powder
1/2 teaspoon baking soda (bi-card soda)
1/4 cup poppy seeds
1. Preheat oven to 180 degrees Celsius
2. Line a muffin tray with papers or silicon muffin cases. I just use a silicon tray because its easiest to wash.
3. Beat sugar, oil, eggs, vanilla zest and orange juice in a jug, with a fork until well combined.
4. Mix flour, baking powder and baking soda in a bowl.
5. Add the wet ingredients to the dry, one third at a time, alternating with the buttermilk. Do not over mix (I still use the same fork). Fold through any extras (I used blueberries).
6. Bake for 20-25 minutes. I turn my tray after 6 minutes and change its shelf position as I do not have a fan-forced oven.
I love these warm out of the oven but they are also nice cooled. As there are only two of us in our house, I wait for all of the muffins to cool and then put them in a large zip-lock bag in the freezer. I zap them for about 30 seconds to reheat (ie. to eat them hot) but you can also let them defrost naturally in the fridge to have later in the day etc.
This is one of the only vintage recipe for muffins that I could find. It is for honey muffins and it comes from The Australian Womens Weekly and it is titled Step-by-Step Cookery by Marguerite Patten in conjunction with Leila Howard. I cannot find a date of publication but judge it to be 60's by the prop-styling inside.