As investors peruse the exchange traded fund universe in their ongoing search for income-generating opportunities, some have stumbled upon a buy-write ETF and its attractive double-digit yields.

Powershares S&P 500 BuyWrite Portfolio ETF (NYSEArca: PBP) offers an impressive 10.25% 12-month yield. The ETF is based off the CBOE S&P 500 BuyWrite Index. It will hold a 80% or more of its assets in common stocks of the 500 companies on the S&P 500 Index and writes, or sells, call options. Specifically, the fund sells one-month at-the-money S&P 500 call options against the portfolio at regular intervals. PBP has a 0.75% expense ratio. [ETF Chart of the Day: PowerShares S&P 500 Buy Write Portfolio]

The buy-write, or covered call, strategy utilizes call options on a position to generate robust income from option premiums. The trader will only lose money if the market price of a stock rises above the exercised price upon maturity of the option, which tends to occur during quickly rising markets. [Buy-Write ETFs Mimic Covered Call Strategy]

An investor would sell a call option above the current price of a security. If the price of the security is below the option upon the expiry date, the investor would pocket the difference. Essentially, a buy-write help provide a cushion from the downside. [ETF Spotlight: Buy-Write Strategy]