Does Smothering Tithe trigger once per draw or once per card drawn when a player draws multiple cards at once?

Smothering Tithe triggers "whenever an opponent draws a card." Under the Comprehensive Rules, drawing multiple cards (such as from Brainstorm or Concentrate) is a sequence of individual card draw events, not a single event. Each card drawn is its own draw event, meaning Smothering Tithe generates a separate trigger for each card. (CR 120.2)

CR 120.2 states that if an effect instructs a player to draw multiple cards, that player performs that many individual draws. Each draw is a discrete event, and any ability that triggers on "drawing a card" checks each draw separately. This is why Smothering Tithe stacks up rapidly in Commander, where wheel effects like Wheel of Fortune can produce 7 triggers per opponent in one turn.

The opponent must respond to (or pay for) each trigger individually. They may pay {2} for each trigger to prevent the Treasure token from being created — but they must make that choice each time the trigger resolves, and triggers from the same draw event all go on the stack at once before any resolve. (CR 603.3, CR 120.2)

Concrete example: An opponent casts Harmonize, drawing 3 cards. Smothering Tithe triggers three separate times, placing three triggers on the stack. The opponent must pay {2} three times (totaling {6}) to prevent all three Treasure tokens. If they pay for only one trigger, you get two Treasure tokens.

Note: In Commander with multiple opponents, if all three opponents each draw from a wheel effect, Smothering Tithe can generate up to 21 triggers (7 per opponent × 3 opponents), making it exceptionally powerful in this format.