Since bundt tins vary significantly in size and proportions, I advise testing for doneness after 35 minutes using a skewer. When poked into the spiced bundt cake the skewer will come out clean, or with a few crumbs attached, if the cake is baked through. If batter is still evident, then continue to bake the cake for another 5 minutes and test again. My caveat to the advice above is that if you know your bundt tin usually takes say, 45 minutes to fully bake a cake, it is better to leave it until closer to this time before the first check. Remember, it is always best to limit the amount of times the oven door is opened when baking cakes.