I usually do the suggestions in my previous question for seasoning the Teflon coated (non stick) bundt pan (buttering and flouring) and I have no problem with that. The problem is with leftover residue,I cannot clean the pan properly. After a few times of cleaning, the surface is hurt and since it is an fairly expensive, I am a little worried. I gave it a long soak in hot water and it didn't work. I also found this question which seems to ask the same thing but the answers are not about cleaning but the other part of the question.
I hope you're using cake release! And you've never actually "seasoned" it (as in covering it with oil and baking it in a very hot oven). If you did season it, that's a problem. I'll get to that in just a second.
Otherwise, all you need is to wash the pan right away in hot soapy water (use a high quality dish soap, ultra cheap ones don't work as well) after each use. If necessary, soak it for a half-hour or so in hot soapy water (as in for hand washing, not machine-dishwashing detergent). Then wash it with a dishcloth. If you still have stuff stuck in crannies, use a soft toothbrush. Dry thoroughly. That's it. If you still have stuff stuck on, use a plastic scrubby sponge like this (my favorite), or this.
Do you absolutely know what surface it is? Unless it says otherwise, don't season it. If it is made by Nordic Ware, look for any model number or anything it says on the box about seasoning or not seasoning. If this is your pan, don't season it. I've got their number. I'll call them if you still have questions, and if this is, in fact, your pan. If you seasoned it, please don't do anything else until we contact the manufacturers. Just catch me in chat, you know I'm almost always there.
There is an answer somewhere on this site (Seasoned Advice) that says that Nordic Ware tells you to season their pans. Please note that that answer refers to pans that DO DOT have a non-stick coating.
What I've found that works for any cake pan is to clean it immediately after removing the cake.
Following my mother's example, as soon as I turn a cake (or layer) out, I wipe out any residue in the pan with a dry paper towel. This gets it out while it is still moist and before it has a chance to harden on the surface of the pan. Once it hardens, it can be quite difficult to remove.
Then, wash as usual.
This has also happened to my pan and it's been soaking and cleaning for two days and still is dirty. So all I've done before is kept soaking and washing till gunk was gone. Nothing else worked.