Can I use Nutralite Butter in baking Cakes and cookies?

After looking that margarine up:

It is advertised as a margarine made of mostly unsatured fats. An ingredient list is not readily found on their website (red flag ;) ) . They also claim to not hydrogenate their fats, so to make a solid margarine you are either looking at https://en.wikipedia.org/wiki/Interesterified_fat (will behave similar to butter when baking) or at some textural tricks that keep oil in a solid block (will likely behave like oil in baking).

If your intention is to cut saturated fats, I would suggest you look up cake recipes that use oil in the first place, and use whatever oil suits your culinary and nutritional taste.

I say you should go for it. In the US, regular household cooks often substitute margarine for butter. Many recipes call for "butter or margarine". Most likely a celebrated chef or food critic would be able to spot the substitution (and be appalled by it), but for most people and most recipes, it works out just fine.

If you are using salted butter instead of unsalted, you should of course leave out any other salt, called out separately, in a cake recipe, but even if that option isn't open (no itemized salt in recipe), your finished cake is very unlikely to be inedible.