In a large mixing bowl mix together the warm water, sugar and yeast. Cover the bowl with a tea towl and let sit for 5 minutes or so til it begins to bubble.
Add the flour, baking powder and salt in that order. Mix it all together with a wooden spoon, then knead and roll into a smooth dough ball for 5 minutes.
Cover the bowl with the tea towel and set aside in a warm dark place for 2 hours til the dough ball has more than doubled in size.
On a lightly floured surface roll out the dough into a log, cut it in half, and cut each half into 8 equal pieces. Roll each piece into a ball.
Press out each dough ball into a 4" circle, then fold in half into a half moon shape.
Place all the buns on the wax paper pieces and lay in bamboo steamers
Bring a pot of 2" of water to a boil, place the steamers on the pot of water and steam for 10 minutes.