A question about a recipe: Nigel Slater's Extremely Moist Chocolate-Beet Cake

It's the difference between using canned pumpkin puree for a pumpkin pie and using fresh pumpkin - some of the people eating it may be able to detect, but most will just enjoy it. If it makes your life easier, go for it.

Honestly, in a baked good, I guarantee you can't tell the difference between using fresh or using canned. One 14-oz can of beets should yield about 1 cup (8 oz) of beet puree. Go for it and save yourself the effort.

I agree with Kristen that fresh is best. But if you must choose canned beets be sure the beets aren't flavored or seasoned in any way and try to use whole rather than sliced

I'd recommend using fresh beets if at all possible (you can boil a whole bunch and save the rest for salads and soups). But it seems like others have had success baking chocolate beet cakes with canned beets, so it's worth a try. See this blog for more details: http://toothandkale.com/2012/02/flourless-chocolate-beet-cupcakes/