What happened

Stock markets came roaring back Tuesday after Monday's turbulent trading session, and as of 10:55 a.m. ET, the S&P 500 was up a solid 2% today. Tech stocks are doing better, with the Nasdaq rising 2.2% -- and certain individual tech stocks are doing even better.

Shares of Roku (ROKU -3.11%) have gained 3.4%, Block (SQ 0.73%) is up 5.1%, and Pinterest (PINS 0.25%) is leading the tech pack higher with a 5.5% gain.

So what

As revealed on the ARK funds website late last night, growth investing icon Cathie Wood returned to the stock market yesterday to make her first purchase of Roku in three weeks, snapping up 97,641 shares of the streaming TV leader.  

Wood was nearly as aggressive buying shares of Block stock, acquiring 92,165 shares, her first purchases of the fintech stock in more than seven weeks. As for Pinterest, Wood hadn't touched it in more than a month and a half. But picking through the tech rubble yesterday, she walked away with 133,779 shares of the social media site.  

Clearly, someone thought yesterday was a buying opportunity.

Now what

But was Wood right to be buying? Her record picking tech stocks hasn't looked great so far this year. Since 2023 began, her flagship ARK Innovation ETF (ARKK 2.08%) is down 10% against a basically flat Nasdaq. Last year, that exchange-traded fund lost 67% -- twice as bad as the 33% loss on the Nasdaq.  

And I get why Wood might have been buying yesterday. Roku stock is down 41.5% over the past 52 weeks. Block is down 32.6%, and Pinterest is only up 4%. If these trains are about to leave the station, there's certainly still time to climb aboard before all the gains have been had.

All I would suggest is that investors mind their step before boarding. None of these three stocks are currently profitable. Pinterest, the most successful, lost $96 million last year, and has lost money in four of the past five years, as has Roku ($498 million last year). Even Block stock -- profitable in three of the last five years -- racked up $540 million in losses in 2022, and might be entering a rough patch.

If you still feel compelled to follow in Wood's footsteps, however, and buy a little tech this week, I think Pinterest is probably the safest bet. While unprofitable on the basis of generally accepted accounting principles (GAAP), the social media site generated a strong $440 million in free cash flow last year -- better than either of the other two stocks on Wood's shopping list.

This gives Pinterest stock a valuation of roughly 37 times free cash flow, which still seems expensive to me, given analyst forecasts for 27% long-term earnings growth. But it's the least risky valuation of the three.