I made a vanilla cake from scratch using this recipe and when I removed it from the pan, I noticed little brown lumps along the bottom and edges the size of BB pellets.    I tasted one of the spots, thinking it was burnt sugar, but it was very hard and very very bitter. I think it tasted like baking powder but also lemony. This is the second time this has happened to me using different recipes. It never happens when I make a chocolate cake.     All the ingredients today were fresh, everything was at room temperature, and the pan was clean. I greased it with Pam and then placed parchment paper circles. I did not have cake flour, so I used AP flour. The batter looked fine and had no lumps in it, I scraped down the sides of the mixing bowl, and nothing tasted off when I licked the spoon. I think it has something to do with adding the baking powder.   What would cause this?  
I have been having this problem on and off. I do think it must have something to do with the baking powder, but it doesnt happen everytime. I keep trying to find an answer but, unless it has happened to you, people think you are crazy.  