In a mixing bowl, combine sugar, oil, and milk. Whisk until sugar dissolves. Add mango puree and mix.
Add dry ingredients and mix. Add lemon juice, mix, and pour into 8 greased ramekins. Cover with aluminum foil.
Add water and steamer rack to pressure cooker. Stack ramekins on rack and close and lock lid. Set pressure cooker to "bake", adjust time to 25 minutes, and press "start/stop".
When done, quick release and make sure all pressure is released before opening lid. Place a toothpick in center of one cake. If it comes out clean, they are done. If not done cook an additional 5-10 minutes. Carefully remove ramekins and allow to cool before serving.