When looking to name something like a company or product...
FIRST: Do an internet search. This will help rule out the ones that are obviously already taken. There are name-search sites that offer a service to do this sort of general check. Most are pay, some are free. Note that this is simply to knock out the obvious ones.
Then there's also a very quick Google search.
Again, this is to quickly knock out the obviously used ones. As you can see, "Simply Cakes" is already used by a few people in one form or another. I'd say keep working on a more unique name.
SECOND: When you've hit the right name that is not already obviously taken (as per your internet research) next thing to do is to check with your local business registration office. They'll have a list of registered names. These names MAY NOT HAVE APPEARED on your internet search, so just because you didn't locate it in step one don't assume you're free and clear.
If you pass this stage and the name you want is available, register it. It's not terribly expensive to do but makes sure that your great name "Dinah's Delicious Deserts" won't get snagged by some other Dinah somewhere down the line and, if it does, you have proof that you were officially first to use it and they can't trump you.
Conversely, it also means that once your business grows and gets more attention, that other Simply Cakes company in Batton Rouge won't sue you for using their name and you have to re-establish your company under a new name.
Another step you'll likely want to do is check the domain name is available. Should you ever want to offer your products online or even simply have an online info presence, it's good to have a unique name that is available.
, for example, has already been grabbed by some domain name grabbing company who'll be happy to let you have it for a whopping lump of cash. Don't. Come up with a unique name that's available and register it with the local business office (protect your assets) and get it's associated domain name (as little as ~ $12/year).