I get about two hours a day where I can actually think. Morning or evening?

Option A is the stronger choice because actual thinking depends first on usable cognitive capacity, not merely on the absence of interruptions. Morning offers the clearest head, which is the harder-to-substitute condition for deep thought. The stated morning drawback—being pulled into a call by nine—is an external, predictable constraint that can be managed by starting earlier, protecting a two-hour block before nine, or rearranging the call. Evening is less reliable because fatigue is an internal barrier: if you are often too tired to start, the uninterrupted window may go unused, and an uninterrupted block you cannot mentally use is worth less than a constrained but usable one. The interruption-free evening has some residual value for lighter tasks, and it could work if energy is reliably managed, but it does not fully satisfy the premise of actually thinking. Therefore, Morning is the better recommendation, with Evening as a fallback only if alertness can be consistently maintained.