Preheat the oven.
Line a 12 muffin tin with paper liners or grease well and keep aside.
In a large bowl, mix well (with a fork) flour, baking powder, baking soda, sugar.
In a microwave safe glass bowl, melt butter (20 seconds).
Add to this cold yogurt, juice and vanilla extract.
Check if this mix has come to room temperature and then add one beaten egg.
(If you add egg to hot melted butter, it will scramble, hence the precaution).
Add the wet ingredients to the dry and lightly combine with a fork until they come together. Do NOT beat or overmix. This will make your muffins rock like.
Spoon a little over a tsp of batter in each muffin liner. Place around a tsp of jam over this and cover with 1-2 tsp of batter, dividing the batter evenly between 12 cups.
Bake at 180 C for 20 minutes or until a skewer inserted comes out clean. (some melted jam may stick to skewer, but that is okay).
Remove and dust with icing sugar.