This is my improved version of a recipe originally found at Love, Swah.
3 tbs vegetable oil (canola or something without much flavor is advised)
3 tbs milk
1/8 tsp vanilla
4 tbs flour
3 tbs brown sugar
1/2 tsp baking powder
1/2 tsp coarse salt
1 tbs (heaping) of dulce de leche (made by boiling a tin of sweetened condensed milk in a pan of water for about 3 hours)
Combine the oil, milk egg and vanilla in a microwave safe bowl and mix well.
Add the remaining dry ingredients and mix to create a batter.
Drop the dulce de leche into the batter -- it will sink to the bottom.
Microwave the dish for about 1 minute 30 seconds or till the batter has solidified into a proper cake.
Eat while hot -- the dulce de leche will have liquified and made a nice sauce for the cake to soak in.