Preheat the oven to 350˚F (170˚C)
In a bowl combine flour and the baking powder. Set aside.
In another large mixing bowl, mix red beans, condensed milk, eggs, and butter. Add the flour mixture to the red bean mixture and mix well with a spoon or spatula.
Grease the 9x13 inch pan and/or line with parchment paper. Pour the mixture in the pan and even out the top. Bake in the oven for 30-40 minutes or until the toothpick comes out clean.
Let the cake cool completely in the pan. Cut into desired size. The cake can stay fresh on the room temperature for 3 days.