Warren Buffett didn't initiate any new positions in 2022's fourth quarter. However, he's still holding onto around 50 stocks in Berkshire Hathaway's (BRK.A 0.68%) (BRK.B 0.93%) portfolio. 

Some of these stocks might have been great picks when the conglomerate first bought them, but wouldn't be such strong buys now. Others, though, still look quite attractive. Here are three Buffett stocks that I think are screaming buys in March.

1. Amazon: Cheaper than it's been in years

Amazon (AMZN 0.58%) truly is available at a historically cheap price right now. The stock trades at only 1.9 times sales. Its price-to-sales multiple hasn't been this low since 2015. I'm a little surprised that neither Buffett nor Berkshire Hathaway's two investment managers are scooping up additional shares of the e-commerce and tech giant at this valuation.

Sure, Amazon's growth has slowed. But that's due largely to temporary factors. Corporate customers, in particular, are watching their spending more closely due to high inflation. Once inflation begins to come down more (which it will, sooner or later), Amazon's growth should again accelerate.

I'm especially bullish about the long-term potential for Amazon Web Services (AWS). Despite massive movement to the cloud in recent years, most IT spending remains on-premises. That should change dramatically over the next 10 to 15 years. AWS stands poised to be a monster growth driver for Amazon, in my view.

The shift to the cloud isn't the only big story for Amazon, though. The company's core e-commerce business still has plenty of room to expand. The company also continues to move into new markets, notably including healthcare, that could boost its profits. 

2. Mastercard: A master innovator

Mastercard (MA 0.30%) stock also appears to be attractively valued. Granted, the stock's forward earnings multiple of 29 might not seem overly appealing. But Mastercard's price/earnings-to-growth (PEG) ratio of under 1.4 is well below the levels of several stocks that Berkshire Hathaway increased its positions in during Q4.

Along with Visa, Mastercard enjoys a duopoly in payment processing. Both stocks are in Berkshire Hathaway's portfolio, and both have great growth prospects. However, Wall Street projects that Mastercard will grow faster than Visa will over the next five years.

Despite economic uncertainty, consumer spending has held up pretty well. Cross-border travel -- a major revenue source for Mastercard -- has also returned to above the levels seen before COVID-19 hit. 

Perhaps the best reason to buy and hold Mastercard stock over the long term is the company's ongoing innovation. Recent examples of Mastercard's innovations include its "buy now, pay later" Installments program, an initiative that's gaining significant momentum. The company is also working with automakers and fintech companies to enable in-car payments.

3. Markel: A "baby Berkshire" with great growth prospects

Markel (MKL 0.64%) stands out as a third Buffett stock that's a bargain right now. Its shares trade at only 17 times expected earnings, and its PEG ratio is a low 0.9.

One of my favorite things about Markel is how much it reminds me of Berkshire Hathaway. The holding company's core focus is on insurance (in this case, specialty insurance). It owns stakes in other public and private companies. Its management has a long-term mindset. All of these things are true for Berkshire as well.

Markel is even sometimes called a "baby Berkshire" because of these similarities. But because its market cap is only a fraction of Berkshire's, it should be able to grow revenue more rapidly than Berkshire. It has certainly been able to do so over the last 10 years.

I think that 2023 could be a strong year for Markel. The company's insurance business remains on track to achieve $10 billion in annual gross written premiums by the end of 2025, along with $1 billion in annual underwriting profits.

And while its Markel Ventures private equity subsidiary didn't add any new companies last year, co-CEO Tom Gayner said in the Q4 conference call that higher interest rates and disruption in fixed-income and equity markets have caused inquiries to increase. He expressed hope that Markel Ventures will identify good opportunities this year.