soften butter, 10 seconds in microwave

stir in 2 tbs of sugar until fluffy and creamy, maybe 30 seconds

add 1/2 egg

then stir in sour cream and few drops of vanilla

stir in flour and baking soda

if you want some crumb topping, in a separate bowl ads 1 tbs butter, 2 tbs flour, 1 tbs brown sugar, and 1 tsp cinnamon. smoosh it together with your fingers.

add crumb layer to top of cup

microwave it. start with 1 minute, then do 10 seconds more until it's done to your liking