No ETF that shorts calls, but one that shorts puts. That it is not in fashion, argues for having better returns than a standard long stock, short calls.You're looking for an ETF that shorts SPX calls. Short spot and short puts = short call. It's just the synthetic (arbitrage). I don't think any exist and it would not draw much interest. Generally funds like to structure "long only" or capped structures (no unlimited risk).
It's not feasible as the fund would have to devote a small % of assets to the strategy to allow for variation margin. I can't imagine any listed fund would be allowed to do so.
But again, I could do several put spreads, with small position in any 1-2 month period.
Thanks.