grammar - Can "recall" be used in an imperative sense?

As a verb, it has an imperative form, but I don't think you'd use it as you did in your example. "Remember" as an imperative can mean (in advance) to remember something later. "Recall" isn't used in advance, and what people have already forgotten they can't reasonably be ordered to remember.

Where a "recall" imperative is used and makes sense is where you are telling someone to recall something you know they can remember, because you want them to reflect on it now. For instance, a history professor might say, "Recall what we learned about Hitler's narcotic abuse last week. With that in mind, what do you think his reaction to this move by the allies might have been?"

In your example, a more likely phrasing would be "John, if you recall, I told you to go shopping."