Grease a 6-hole silicone muffin pan.
Sift the flour into a medium bowl
Add a pinch of salt and the caster sugar.
In a jug, combine the vegetable oil, egg, milk and vanilla extract.
Add to the dry mixture and stir to only just combine.
Place a spoonful of the mixture in each muffin hole and make an indent in the centre.
Fill each indent with a generous 1/2 teaspoon of strawberry jam.
Cover the jam with the remaining muffin mixture.
Place the silicone muffin tray elevated with a wire rack into cooker
Cook for an hour on HIGH in the with a tea towel under the lid
Remove from the cooker and allow to cool a bit.
Meanwhile, melt the butter.
Combine the extra sugar and the cinnamon in a large bowl.
When the muffins are cool enough to handle, brush each muffin with the melted butter
Roll in the cinnamon sugar.
Serve while still a little warm.