I have had success making a naturally dyed pink cake...
- Puree
The color with raspberries is better, but I have used strawberry puree too. The recipes with puree (even simmered, reduced, and strained) always seem a bit too wet in the end, to me. What a sad waste of good ingredients. Here are the posts on my blog of cake with raspberry puree and one with strawberry puree. The people I fed liked it, the flavor was very pleasant. But, I wasn't totally pleased with the texture.
- Freeze Dried Strawberries/Raspberries
Again the color with raspberries is a little bit more strong, but both work! To color the batter I processed the fruit in a blender until powdered. Then, I sifted the powder to remove any seeds or larger pieces. Finally, I added the sifted powder to the dry ingredients of a white cake recipe. This is my preferred method (over puree). I also posted the results of this process on my blog.
One last thing...do not bother with fresh beets. I have not tried using canned, but the fresh beets DO NOT WORK. I tried it many ways, pureed, steeped in the wet ingredients then strained, I made a very acidic batter hoping that would help...none of it worked. They also tasted faintly dirty. Blegh. Every time the batter would be gorgeously pink, but, like a sick magic trick, the color would cook out.
I would still love to find a way to make a pink cake that is very intense, but the powdered freeze dried fruit does result in a pretty, soft pink. I hope this helps!