Preheat the oven to 350°F, then grease and flour the baking pan and set aside.
Combine the flour, salt, and baking powder.
Whisk, mash or blend the plantains till fairly smooth.
Use a hand whisk to cream the butter and sugar for 2 to 3 minutes. Add the eggs one at a time and cream together until just combined. Add the Yogurt and vanilla and whisk together.
Mix the mashed plantains with the creamed butter and add the mixture to the dry ingredients (flour, salt, and baking powder). Fold a couple of times until well mixed. (don't over mix).
Stir in the milk and mix till combined.
Pour the batter into the prepared baking pan. Smooth out the surface of the batter and bake for 50 minutes to 1 hr or till a tester or toothpick inserted into the middle of the cake comes out clean.