Do you trim your cakes to make them perfectly level? If not, they are going to have that 'arch.'
Hmmm...are you leveling the bottom before you invert the cake onto your board? If not, then yes, I can see the cake always having a crown.
Otherwise, I'm not sure how to alleviate your problem. I'm not sure how you ice a cake, spatula, scraper, other method?
When I ice a cake, I use a bench scraper (..dough knife, whatever you like to call it!) It's hard to explain my process other than to say "I put on lots of icing, then scrape off the excess!" I start by covering the entire cake in icing. Then I go back and use my scraper to remove the excess on the sides, smoothing and creating a nice crisp corner. I then smooth the top knocking of the corners and then centers of the top of the cake. If you are not careful in this process, you can scrape excess icing to the center of the cake...forming a crown. You must use steady pressure to pull the icing down to a consistent level all the way across the surface. This can sometimes leave blade marks in your icing on the top of the cake. If you end up with blade marks, look up Melvira's Method for smoothing using a Hi-Density Foam roller to smooth your icing!
HTH!
The problem (sorry if I wasn't clear) is the cake looking like it settles on the sides and then me ending up with a square cake from every angle but the top. I do level every one of my cakes but For some reason it's only on the square cakes that I get an arch and the thing looks like I didn't level it on top. I have a good example of this in my photos. The black and white wedding cake.
i looked at your photo and i see what you're saying. is the icing the same thickness? does it look level before you ice it? maybe you're putting more filling in the center vs. the edges. i don't really know- i avoid square cakes like the plague- i'm impressed with your corners 
i've looked at the tutorial on doing square corners, but i can't do it.
Could it be you're not letting the cake rest 10 minutes in the pan before inverting? I find my cakes do not hold their shape as well if I rush the cooling time.
Are you using the Wilton large cake leveler? That thing bends and warps as you cut through the cake and that could be why you have a dome after you have torted. I would test it out first to see if this is the problem. Take the top off a cake you have just cut and lay it on the counter to see if it's laying flat. If it's not, then you know it's your leveler. Otherwise maybe you're putting too much filling in the middle or not letting the filling settle before icing.
I'm not sure, just throwiing ideas out there to see which it could be. 
How much filling are you putting in there? The middle tier seems to have a shadow across the middle that looks like a LOT of filling. If the filling isn't level (and most people tend to spread it out towards the side, which results in thick-middle-thin edges), then your cake isn't going to be level. If this is the case, you need to be sure to spread it evenly across the entire cake. If that shadow is the filling .... I'd reduce the amount of filling you're using.
An example of what I mean: If you've ever seen a pizza being made .... they pour the big scoop of sauce in the middle of the dough and then spread it out toward the edges. I find there is still a big glop in the center (making it messy and drippy when I'm trying to eat it!) and hardly any at all at the edges. 
I luv doing square cakes. I find them easier to work with than round ones. Magic Line pans make a big difference, too.
I find that you still have to "build up" the top like you have to the corners. I think that the uneveness come s from pulling to much frosting off the top when finishing. I've done it. I'll frost my cake and then let it sit in the fridge for a while to let the frosting set up, then I'll have a more solid corer to make sure it is level (use a small level) and then build up if i have to. H.ope theat helps
Quote by @%username% on %date%
%body%