If you bake a cake at a lower temperature below 350 F then the cake can take longer to cook.
Also baking a cake at lower temperatures can slow the spring in the leavening, which prevents a dome from forming on your cake.
Cakes should be baked at a temperature of at least 350 F so the cake cooks properly.
If you increase the temperature then the cake can cook too fast and then crack as well.
You can however bake the cake at 250 F degrees until the cake sets and then increase the oven temperature to 350 F so that the cake cooks properly.
Baking a cake at 350 F takes around 30 to 35 minutes for a 9 " round cake and 50 to 55 minutes for a 14" or larger cake.