Recently, a question came up about where one can find vegan birthday cakes in the valley. Admittedly, there aren't a lot of options for store-bought cakes here. That I am aware of, anyway.
Most grocery store bakeries are staffed with people who do not understand what 'vegan' means and who do not have experience baking vegan foods. They might slip in some eggs and dairy without realizing those are no-no's. And honestly, I've never been a fan of grocery store cakes, plus vegan baking takes a little bit of practice that they just don't have. I just don't think you'll get something of quality if you tried to order from a regular grocery store bakery. Which is crazy, because vegan baking is really not that hard. Trust me. Anyway, I personally would not attempt a regular grocery store bakery.
Instead, you can try one of these options (not in any particular order).
1. While I poo-pooed the idea of ordering a cake from a grocery store, there is one possible exception to that. I would try ordering from Whole Foods' bakery. Don't be surprised if your success with this depends on the bakery staff at your local store. Some are more experienced with vegan foods than others. I know the WF bakery I go to regularly offers a vegan peanut butter fudge, and the deli case often has 5-6 vegan goodies. But cakes might be another matter altogether. Now, while you are talking to them about options, they might direct you to Fabe's brand vegan cakes. I don't recommend them.
Admittedly, I refused to try the chocolate cake because I don't like chocolate cake, and I haven't tried the banana cake. But I did try their carrot cake a few times. Fabe's cakes are made and then frozen and shipped out to stores before being sold to you. I don't know if these cakes taste ok fresh, but I have had the carrot cake a couple of times now and both times it was dry and blah. I will not buy them again. After trying the carrot cake, I just couldn't get myself to fork over the money for the banana. But who knows, maybe you'd like them? They are there if you want to try them. But please, try them when you are not celebrating something special. See if you like them before you go foisting them onto unsuspecting friends and family at a party. What's important here is that you never knowingly feed anything that you know tastes crappy to non-vegans. That is a cardinal sin. It gives our food an undeserved bad rap.
Oh, gawd, I am certainly going to vegan hell for dissing a vegan product. In theory, I am 100% behind and support all vegan products, because I know someone out there must like them even if I don't and because they are certainly trying to be helpful. But I have to be honest, the last thing I want is non-vegans judging the vegan diet on less-than-tasty foods. That is counter to my cause. With that in mind, I do have to add one tiny little disclaimer for my review of Fabe's Carrot Cake. My family has that yummy carrot cake recipe that I recently veganized. I have never liked another carrot cake ever (and don't you dare put nuts or dried fruit in carrot cake!). And believe me, I have tried as many as I could get my fork on. And it's easy to say that I have been very spoiled lately with homemade vegan cakes thanks to Isa and Terry's Vegan Cupcakes Take Over the World cookbook. So it is possible I am biased in this matter.
2. Ok, another store-bought option would be Sprinkles in Scottsdale. They sell all sorts of cupcakes including vegan red velvets. The vegan red velvet cupcake is a regular menu option, but if you need a certain quantity, it is best to call ahead. I believe they also have random seasonal vegan flavors. I have not yet had the pleasure of a Sprinkles cupcake myself, but one of these days I will get there. Their website indicates they do special orders, and they can decorate your cuppers for you too. Cupcakes are much cooler than sheet cakes, you know.
3. Very similar to Sprinkles is Cupcakes, also in Scottsdale. Their standard vegan cupper is lemon flavored. Same dealio with the seasonal flavors and special order options. I have not tried them yet either, but I'm looking forward to it.
4. If I were looking for cakes or some kind of party dessert, I would also call on Green and Loving Hut and see what they could offer you. They are the only two completely vegan restaurants left standing, and both of them have vegan dessert items in their repertoire. Green is probably your better bet, since they actively cater events and I've seen a wider variety of desserts as specials on their menu.
5. If there is time to make something 'homemade' but you need something cheap and easy and you don't want to have to track down any obscure ingredients, the Cherrybrook Farms cake mix (vanilla or chocolate) is easy to make and is vegan. You can find the mixes at Sprouts, Whole Foods, and even Fry's Marketplace (sometimes in the natural section). All you need is some water and Earth Balance vegan margarine to add to the cake mix. I have made these cakes several times and they are good. No one ever realizes the cake came from a box.
They have frosting mixes as well, chocolate or vanilla. [I do not recommend the ready-to-spread jar of frosting. The last jar I bought was more like sticky icing rather than frosting and didn't spread at all.] The frosting mix only requires some kind of non-dairy milk (I always recommend Blue Diamond Almond Breeze SWEETENED Almond milk for baking [vanilla or chocolate flavored depending on what you are making], but any non-dairy milk should be fine) and Earth Balance vegan margarine.
If you want to up the ante on these cake mixes, I highly suggest making the Cherrybrook Farms mixes into cupcakes with the cream cheese frosting from my carrot cake. It's still easy and the frosting is a winner. Delicious!
I hope this helps you track down a good cake dessert. Good luck!