Steep rosemary in hot milk for 5 minutes and set aside to cool.
Cream the butter and sugar together until light and fluffy.
Add the eggs and vanilla and mix well.
In a bowl mix the flour, salt, and baking powder together.
Add half of the flour mixture to the wet mixture and mix until just combined.
Mix in the room-temperature infused milk.
Add the remaining half of the flour mixture and mix until just combined.
Pour into cake pans and bake for 25-30 minutes at 170ºC.
Let cake cool completely before frosting.